- !important
- .gitignore
- .htaccess
- .htpasswd
- .NET
- .NET Framework
- /dev/null
- /now page
- /uses page
- 1 Percent Rule
- 100
- 101
- 102
- 109
- 110
- 11ty
- 143
- 1NF
- 1–9–90 Rule
- 20
- 200
- 201
- 202
- 203
- 204
- 205
- 206
- 207
- 21
- 22
- 220
- 226
- 23
- 25
- 2FA
- 2NF
- 300
- 301
- 302
- 303
- 304
- 305
- 306
- 307
- 308
- 389
- 3NF
- 400
- 401
- 403
- 404
- 405
- 406
- 407
- 408
- 409
- 410
- 411
- 412
- 413
- 414
- 415
- 416
- 417
- 418
- 421
- 422
- 423
- 424
- 425
- 426
- 428
- 429
- 431
- 443
- 451
- 500
- 501
- 502
- 503
- 504
- 505
- 507
- 511
- 53
- 70
- 79
- 8.3
- 80
- 80/20 Rule
- 8008
- 8080
- 8443
- 88
- 90/90 Rule
- 992
- 993
- 995
- A
- A List Apart
- A/B testing
- A11Y
- AAA
- AAAA
- Ableism
- Above the fold
- Absolute domain name
- Abstract data type
- Abstraction
- Accelerated Mobile Pages
- Accept-CH
- Acceptance criteria
- Acceptance test-driven development
- Acceptance testing
- Access control
- Access Control List
- Access key
- Access logs
- Access token
- Accessibility
- Accessibility Conformance Report
- Accessibility Conformance Testing
- Accessibility decay
- Accessibility Maturity Model
- Accessibility Object Model
- Accessibility Toolkit
- Accessibility tree
- Accessible Rich Internet Applications
- ACE
- ACID
- Acid tests
- ACK
- ACL
- ACM
- Acq-hiring
- Acqui-hiring
- ACR
- ACSS
- ACT
- Action item
- ActionScript
- Active monitoring
- Active redundancy
- Active Server Pages
- Active Users
- ActiveX
- Activity Streams
- ActivityPub
- Actual value
- Adaptive
- Adaptive loading
- Adaptive technology
- ADC
- Addon
- Address Resolution Protocol
- Adobe ColdFusion
- Adobe Dreamweaver
- Adobe Flash
- Adobe Photoshop
- ADR
- ads.txt
- ADT
- Advanced Encryption Standard
- Advanced Package Tool
- Advanced Perceptual Contrast Algorithm
- Advanced Persistent Threat
- ADX
- AEO
- AES
- Affordance
- Agile
- Agile Manifesto
- Agile Release Train
- AIC triad
- AirMosaic
- AJAX
- AKM
- ALA
- Alerting
- Alertmanager
- ALGOL
- Algorithm
- Algorithmic Language
- Aliasing
- Almost-standards mode
- Almost-strict mode
- Alpha blending
- Alpha compositing
- ALPN
- Alternate style sheet
- Amaya
- Amazon Resource Name
- Amazon Route 53
- Amazon S3
- Amazon Silk
- Amazon Simple Queue Service
- Amazon Simple Storage Service
- Amazon SQS
- Amazon Virtual Private Cloud
- Amazon VPC
- Amazon Web Services
- Ambient declaration
- AMD
- Amdahl’s Law
- American National Standards Institute
- American Standard Code for Information Interchange
- AMP
- Analytics
- Anchor
- Angular
- AngularJS
- Animation
- Anonymous block box
- Anonymous block element
- Anonymous function
- Anonymous inline box
- Anonymous inline element
- Anonymous text
- ANSI
- Anti-aliasing
- Anti-pattern
- AOM
- AOMedia Video 1
- AOP
- Apache
- Apache CloudStack
- Apache Groovy
- Apache HTTP Server
- Apache Maven
- Apache Subversion
- Apache Tomcat
- Apache Weex
- APCA
- API
- API evangelism
- API gateway
- Apollo
- Apollo Graph
- Apollo GraphQL
- App
- App shell
- Apple Safari
- Apple Universal Access
- Applet
- Application
- Application context
- Application Default Credentials
- Application programming interface
- Application Security Verification Standard
- Application shell
- Application-Layer Protocol Negotiation
- APT
- AR
- Arbitrary code execution
- Architectural knowledge management
- Architecture Decision Record
- Arena
- Argument
- ARIA
- ARIA roles
- Arity
- ARN
- ARP
- Arrange, act, assert
- Array
- Arrow function
- ART
- ASCII
- ASI
- asm.js
- ASP
- ASP.NET
- Aspect ratio
- Aspect-oriented programming
- AssemblyScript
- Assignment
- Assistive technology
- Assistive Technology Service Provider Interface
- Association for Computing Machinery
- Astro
- ASVS
- Asynchronous
- Asynchronous JavaScript and XML
- Asynchronous Module Definition
- AT
- at
- AT Protocol
- at-keyword
- at-rule
- AT-SPI
- ATAG
- ATDD
- ATK
- Atlassian Bitbucket
- Atlassian Jira
- Atom
- Atomic CSS
- Atomicity, consistency, isolation, durability
- Attribute
- Attribute minimization
- Audit log
- Audit trail
- Augmented reality
- Authenticated Data Experiment
- Authenticated Transfer Protocol
- Authentication
- Authoring tool
- Authoring Tool Accessibility Guidelines
- Authorization
- Auto Forms Mode
- Automagic
- Automatic Semicolon Insertion
- Automation
- Autonomous custom element
- AV1
- AV1 Image File Format
- Availability Zone
- AVIF
- Away team
- Awesome list
- AWK
- AWS
- axe
- AZ
- BA
- Babel
- Back/forward cache
- Backend
- Backend for Frontend
- Backlink
- Backup
- Backup redundancy
- Backward-compatibility
- Bad Neighborhood
- Bada
- Bandwidth
- Banner
- Bar
- Barrel file
- Barrierefreie-Informationstechnik-Verordnung
- Base64
- Baseline
- Bash
- Basic access authentication
- Basic Multilingual Plane
- BAU
- Baud
- BBCode
- BCP
- BDD
- Bearer
- Bearer authentication
- Bearer token
- Behavior
- Behavior-driven development
- Below the fold
- BEM
- Benchmark
- Best Current Practice
- Best practice
- Between-groups design
- Between-subjects design
- BFC
- BFCache
- BFF
- BFS
- BGP
- BHO
- Bidi
- Bidi algorithm
- Bidi isolation
- Bidirectional
- Bidirectional isolation
- Big Bang
- Big data
- Big integer
- Big O notation
- Binary chop
- Binary compatibility
- Binary large object
- Binary metric
- Binary number
- Binary search algorithm
- Binary tree
- Binary-code compatibility
- Binding
- Birthday attack
- Birthday problem
- Bit blit
- Bit block transfer
- Bit manipulation
- BitBLT
- Bitbucket
- Bitmap
- BITV
- Black hat
- Black mode
- Black-box testing
- Blacklist
- Blink
- Blisk
- Blitting
- Blob
- Block
- Block box
- Block cipher
- Block container
- Block container box
- Block container element
- Block element
- Block Element Modifier
- Block flow
- Block formatting context
- Block-level box
- Block-level element
- Blockification
- Blog
- Blogging
- Blogosphere
- Bloom filter
- BMP
- BOM
- Bookmark
- Bookmark icon
- Bookmarklet
- Boolean
- Bootstrap
- Border
- Border Gateway Protocol
- Bottom-posting
- Bottom–up design
- Bounce rate
- Bound variable
- Boundary value problem
- Bounding box
- Bourne shell
- Bower
- Box
- Box model
- Box model hack
- Boyscout Rule
- Bracket notation
- Braille (⠃⠗⠁⠊⠇⠇⠑)
- Branch
- Branch coverage
- Branch predication
- Branching
- BREAD
- Breadcrumb
- Breadth-first search
- Breakpoint
- Brewer’s Theorem
- Bring Your Own License
- Broken link
- Brotli
- Browse mode
- Browse, read, edit, add, delete
- Browser
- Browser detection
- Browser engine
- Browser extension
- Browser Helper Object
- Browser sniffing
- Browser testing
- Browser War
- Browsing
- Browsing context
- BTR
- Buffer
- Bug
- Bug tracking system
- Bugfix
- Bugzilla
- Build verification test
- Build-time render
- Bulletin Board Code
- Bun
- Bundled HTTP Exchanges
- Bundling
- Bus factor
- Bushnell’s Law
- Business as usual
- BVT
- BYOL
- Byte order mark
- Bytecode
- Bézier curve
- C2PA
- CA
- Cache
- Cache busting
- Cache eviction
- Cache partitioning
- Cache poisoning
- Cache timing attack
- CAI
- California Consumer Privacy Act
- Call stack
- Call to action
- Callback
- Callback queue
- Camel case
- Camino
- Canary
- Candidate Recommendation
- Cannibalization
- Canonical equivalence
- Canonical link
- Canonical Name
- Canvas
- CAP Theorem
- CAPTCHA
- Card sorting
- Cardinality explosion
- Caret
- Caret browsing
- Caret navigation
- Carousel
- Cart
- Cascade
- Cascading HTML Style Sheets
- Cascading Style Sheets
- Case
- Case folding
- Case mapping
- catch
- CBD
- CBSE
- CC/PP
- CCPA
- CCT
- ccTLD
- CD
- CDATA
- CDN
- CDP
- CDUI
- CERT
- Certificate
- Certificate authority
- Certificate revocation list
- Certificate signing request
- CES
- CFML
- CGI
- Chaining
- Change list
- Change set
- Changeset
- Channel messaging
- Chaos engineering
- Character
- Character data
- Character encoding
- Character entity reference
- Character reference
- Character set
- Charset
- Chartjunk
- Checkbox hack
- CheiRank
- chmod
- chown
- Chrome
- Chrome Custom Tabs
- Chrome DevTools
- Chrome DevTools Protocol
- Chrome OS
- Chrome User Experience Report
- ChromeVox
- Chromium
- CHSS
- Churn
- Churn rate
- CI
- CI/CD
- CIA triad
- CIDR
- Cipher
- CircleCI
- Cisco Discovery Protocol
- CJS
- CL
- Class
- Class variable
- Classitis
- Classless Inter-Domain Routing
- CLDR
- Clearance
- Clearfix
- CLF
- CLI
- Click
- Click-through rate
- Clickjacking
- Client
- Client Hints
- Client side
- Client-side rendering
- Clipping
- Cloaking
- Clojure
- Clone detection
- Closure
- Cloud
- Cloud computing
- Cloud storage
- CloudStack
- CLS
- Cluster
- CMF
- CMP
- CMS
- CMYK
- CNAME
- CNAME cloaking
- Coalescing
- Coalition for Content Provenance and Authenticity
- COC
- Code
- Code coverage
- Code debt
- Code golf
- Code of conduct
- Code point
- Code refactoring
- Code review
- Code smell
- Code splitting
- Codeline
- CodePen
- Coder
- Coding by Convention
- Coding guidelines
- COE
- COEP
- CoffeeScript
- COGA
- COGA TF
- Cognitive and Learning Disabilities Accessibility Task Force
- Cognitive complexity
- Cognitive disability
- Cold data
- ColdFusion
- ColdFusion Markup Language
- Collapsed margin
- Color blindness
- Color circle
- Color management
- Color scheme
- Color wheel
- Color, Material, Finish
- Combinator
- Comma-Separated Values
- Command
- Command-Line Interface
- Command-Query Responsibility Segregation
- Command-Query Separation
- Comment
- Commit
- Common Gateway Interface
- Common Locale Data Repository
- Common Log Format
- Common Object Request Broker Architecture
- Common Vulnerabilities and Exposures
- Common Vulnerability Scoring System
- CommonJS
- CommonMark
- Community of practice
- Compared to what?
- Compass
- Compatibility
- Compatibility equivalence
- Compatibility mode
- Compiler
- Compiling
- Complementary colors
- Component
- Component library
- Component-based development
- Component-based software engineering
- Component-driven user interface
- Composite Capability/Preference Profiles
- Compression
- Computational irreducibility
- Computed value
- Computer programming
- Concurrency
- Concurrent Versioning System
- Concurrent Versions System
- Condition coverage
- Condition variable
- Conditional
- Conditional Comments
- Cone of Uncertainty
- Confidence interval
- Confidence testing
- Confidentiality agreement
- Confidentiality, integrity, and availability
- Configuration drift
- Conflict of interest
- Conflict-free replicated data type
- Conformance
- Conformance testing
- Confounding variable
- Connection draining
- Consent management platform
- Consistency
- Consistent hashing
- Console
- Constant
- Constructor
- Container
- Container query
- Containerization
- Containing block
- Containment
- Content
- Content Authenticity Initiative
- Content box
- Content category
- Content Credentials
- Content delivery network
- Content management system
- Content MathML
- Content negotiation
- Content network
- Content optimization
- Content projection
- Content Security Policy
- Content sniffing
- Context switch
- Continuous delivery
- Continuous deployment
- Continuous integration
- Continuous media
- Contrast
- Control flow
- Control stack
- Convention over Configuration
- Conventional Commits
- Conversion
- Conway’s Law
- Cookie
- Cookie banner
- Cookie consent
- Cookie hijacking
- Coordinated Universal Time
- COP
- CORB
- CORBA
- Core Web Vitals
- CORP
- Corporate design
- Corporate identity
- Correction of Errors
- CORS
- Cost-per-click
- Country code top-level domain
- Coupling
- CPA
- CPC
- CPH
- CPM
- CQRS
- CQS
- CR
- CRA
- Craft
- CRAP
- Crawler
- Crawler trap
- Crawling
- CRDT
- Create React App
- Create, read, update, delete
- Create, replicate, append, process
- Critical CSS
- Critical design
- Critical path
- Critical path analysis
- Critical path method
- Critical rendering path
- CRL
- CRM
- cron
- Cron job
- Crontab
- Cross-Origin Read Blocking
- Cross-Origin Resource Policy
- Cross-Origin Resource Sharing
- Cross-Origin-Embedder-Policy
- Cross-site request forgery
- Cross-site script inclusion
- Cross-site scripting
- Cross-site WebSocket hijacking
- CRP
- CRUD
- Cruft
- CrUX
- Cryptography
- CSCS
- CSP
- CSR
- CSRF
- CSS
- CSS Action Committee
- CSS framework
- CSS lock
- CSS Module
- CSS Naked Day
- CSS Object Model
- CSS pixel
- CSS preprocessor
- CSS Samurai
- CSS Zen Garden
- CSS-in-JS
- CSS-Tricks
- CSSOM
- CSV
- CSWSH
- CTA
- CTR
- Cumulative Layout Shift
- curl
- Curly’s Law
- Currying
- cursive
- Custom data attribute
- Custom element
- Custom property
- Customer Effort Score
- Customer relationship management
- Customized built-in element
- Customized Scripting in C#
- Cutting the mustard
- CVE
- CVS
- CVSS
- Cyan, magenta, yellow, and key
- Cybersquatting
- Cycle time
- Cyclomatic complexity
- D3.js
- DAD
- Daemon
- DAG
- Daily
- Daily Active Users
- Daily scrum
- DAM
- Dark mode
- Dark pattern
- Dark Web
- Darknet
- Dart
- DAST
- Data
- Data build tool
- Data center
- Data control language
- Data definition language
- Data lake
- Data localization
- Data loss
- Data management platform
- Data manipulation language
- Data masking
- Data obfuscation
- Data query language
- Data residency
- Data storage
- Data stream management system
- Data swamp
- Data type
- Data visualization
- Data warehouse
- data-* attribute
- Database
- Database engine
- Database index
- Database language
- Database management system
- Database server
- Database shard
- DAU
- DAVE
- DBC
- DBMS
- dbt
- DCE
- DCL
- DCVS
- DDA
- DDD
- DDL
- DDoS
- Dead Internet theory
- Dead letter queue
- Dead-code elimination
- Debugging
- Declaration
- Declaration block
- Decoration
- Decryption
- Deep linking
- Deep Web
- Defect
- Defect tracking system
- Definition of done
- Delete, add, view, edit
- Demilitarized zone
- Denial of service
- DENIC
- Deno
- Denormalization
- Dependency
- Dependency injection
- Dependency Inversion Principle
- Deployment
- Deployment environment
- Deprecated
- Deprecation
- Deprecation trial
- Depth-first search
- Descendant
- Descender
- Deserialization
- Design
- Design by Contract
- Design debt
- Design language
- Design strategy
- Design system
- Design token
- Design vocabulary
- Destructuring
- Deterministic random bit generator
- Developer advocacy
- Developer experience
- Developer relations
- Developer tools
- Development and operations
- Development team
- DevEx
- Device orientation
- Device pixel
- DevOps
- DevOps Research and Assessment
- DevRel
- DevTools
- DFS
- DHCP
- DHTML
- Dialog box
- Digital asset management
- Digital rights management
- DIP
- Directed acyclic graph
- Directionality
- Disabilities, Opportunities, Internetworking, and Technology
- Disability Discrimination Act
- Disciplined Agile Delivery
- Disjoint sets
- Display advertising
- Display resolution
- Distributed Concurrent Versions System
- Distributed persistent rendering
- Distributed version control system
- Dither
- Dithering
- Divitis
- Django
- DKIM
- DLL
- DLR
- DMARC
- DML
- DMP
- DMZ
- DNAME
- DNS
- DNS over HTTPS
- DNS root zone
- DNS spoofing
- DNSKEY
- DNSSEC
- DO-IT
- DocBook
- Docker
- DOCTYPE
- Document directive
- Document Object Model
- Document Style Semantics and Specification Language
- Document type declaration
- Document type definition
- Documentation
- DoD
- DoH
- Dojo
- DOM
- DOM clobbering
- Domain
- Domain expert
- Domain name
- Domain name server
- Domain Name Service
- Domain Name System
- Domain Name System Security Extensions
- Domain sharding
- Domain squatting
- Domain-Based Message Authentication, Reporting, and Conformance
- Domain-driven design
- DomainKeys Identified Mail
- Don’t Repeat Yourself
- Doorway page
- DORA
- DORA metrics
- DoS
- Dot file
- Dot notation
- Dot-agnostic
- Dots per inch
- Double
- Downstream
- Downtime
- Downward-compatibility
- DPI
- DPR
- DQL
- DRBG
- Dreamweaver
- Drift
- Driver
- DRM
- DRY
- DSMS
- DSSSL
- DTD
- Duck typing
- Duncan’s taxonomy
- Dup
- Duplicate code
- DVCS
- DW
- DWH
- DX
- Dynamic application security testing
- Dynamic color
- Dynamic Host Configuration Protocol
- Dynamic HTML
- Dynamic Language Runtime
- Dynamic password
- Dynamic scope
- Dynamic typing
- Dynamic website
- Dynamic-link library
- DYOR
- Dyslexia
- E2E
- EAA
- EAT
- EBCDIC
- EBM
- ECB
- Eclipse
- ECMA
- Ecma International
- ECMAScript
- Ecommerce
- ECT
- Edge
- Edge caching
- Edge computing
- Edge coverage
- Edge-side rendering
- Edit distance
- Editor
- EditorConfig
- EFF
- Effective Connection Type
- Effectiveness
- Efficiency
- EIP
- Elastic
- Elastic IP
- Elastic Network Interface
- Elasticity
- Elasticsearch, Logstash, and Kibana
- Electron
- Electronic codebook
- Electronic Frontier Foundation
- Element
- Eleventy
- ELF
- ELK
- else
- Elvis operator
- Em
- Emacs
- Email address
- Email spoofing
- Embedded content
- Embedded style sheet
- Ember.js
- EMD
- EME
- Emmet
- Empiricism
- Empty element
- Empty string
- Encapsulation
- Encrypted Media Extensions
- Encryption
- End of file
- End of life
- End of line
- End tag
- End-to-end testing
- ENI
- Entity
- Entity graph
- Entity identifier
- Entity reference
- Environment isolation
- Environment variable
- EOF
- EOL
- Ephemeral storage
- Epic
- Epoch time
- Equal-width typeface
- Equality Act 2010
- Error
- Erwise
- ES
- ES Modules
- ES4
- ES6
- ESM
- ESR
- Ethics
- Etiquette
- ETL
- European Accessibility Act
- European Computer Manufacturers Association
- Event
- Event handler
- Event loop
- Event-driven architecture
- Eventual consistency
- Even–Odd Rule
- Evidence-Based Management
- Exact-match domain
- Exception
- Exception handling
- Exception handling syntax
- Execution stack
- Exit code
- Exit status
- Expertise, authoritativeness, trustworthiness
- Express
- Extended Binary Coded Decimal Interchange Code
- Extended Log Format
- Extensible Application Markup Language
- Extensible HyperText Markup Language
- Extensible Markup Language
- Extensible Stylesheet Language
- Extensible Stylesheet Language Transformations
- External
- Extract, transform, load
- Extreme programming
- Eye tracking
- FaaS
- Facade pattern
- Fagan inspection
- Fagan testing
- Failover
- Fallback
- False negative
- False positive
- Falsy
- fantasy
- Fat footer
- Favelet
- Favicon
- Favorite
- Favorite icon
- FCP
- Feature creep
- Feature detection
- Feature phone
- Feature testing
- Federal Information Processing Standard
- Federated Learning of Cohorts
- Federation
- Fediverse
- Feed
- Feed reader
- Fetch API
- FID
- FIFO
- Fifth Rule of ARIA
- Figma
- File
- File extension
- File locking
- File manager
- File system
- File Transfer Protocol
- Filename extension
- Filter primitive
- Fingerprinting
- FIPS
- Firebird
- Firefox
- First Contentful Paint
- First CPU Idle
- First in, first out
- First Input Delay
- First Interactive
- First Meaningful Paint
- First normal form
- First Paint
- First Public Working Draft
- First Rule of ARIA
- First-class function
- First-order function
- Fitts’s Law
- Fixed
- Flame graph
- Flash
- Flash of faux text
- Flash of invisible text
- Flash of unstyled content
- Flash of unstyled text
- Flash Player
- Flat design
- Flesch–Kincaid readability tests
- Flex
- Flexbox
- Float
- FLoC
- Flock
- FLOSS
- Flow content
- Flow of control
- Fluent Design System
- Fluid
- Flutter
- Flynn’s taxonomy
- FMP
- FOAF
- Focus
- Focus mode
- FOFT
- FOIT
- Fold
- Folksonomy
- Font
- Font Awesome
- Font block period
- Font failure period
- Font matching
- Font subsetting
- Font swap period
- Foo
- Foobar
- for
- foreach
- Foreign key
- Forest
- Fork
- Form
- Formatting context
- Formatting Output Specification Instance
- Forms mode
- Forward proxy
- Forward secrecy
- Forward-compatibility
- FOSI
- FOSS
- FOUC
- Fourth Rule of ARIA
- FOUT
- FPS
- FPWD
- FQDN
- Fragment identifier
- Frame
- Frame busting
- Frame rate
- Framekiller
- Frames per second
- Frameset
- Framework
- Free and Open Source Software
- Free Software Foundation
- Free variable
- Free/Libre and Open Source Software
- Friend of a Friend
- Frontend
- FrontPage
- FS
- fs
- FSF
- FTP
- FTP over SSH
- FTP Secure
- FTP-SSL
- FTPS
- Fuchsia
- Fugu
- Full Service
- Full Stack
- Full stack developer
- Fully qualified domain name
- Function
- Function as a service
- Function binding
- Function coverage
- Function overloading
- function*
- Functional programming
- Functional testing
- FutureSplash
- Fuzz testing
- Fuzzing
- GA
- GAAD
- Gamma
- Gang of Four
- Garbage collection
- Garbage in, garbage out
- Gateway
- Gatsby
- GCP
- GDE
- GDPR
- Gecko
- Gem
- Gemfile
- General Availability
- General Data Protection Regulation
- General Image Manipulation Program
- General Responsibility Assignment Software Patterns
- Generator
- Generator function
- Generic programming
- Generic top-level domain
- GeoCities
- Geocities-izing
- Geofence
- Geolocation API
- Geturl
- GIF
- GIGO
- GIMP
- Git
- Git flow
- Git submodule
- GitFlow
- GitHub
- GitHub Copilot
- GitLab
- Gitmoji
- GIYF
- Global
- Global Accessibility Awareness Day
- Global object
- Global scope
- Global variable
- Globalization management system
- Globally unique identifier
- Glyph
- GMS
- GNU
- GNU General Public License
- GNU Project
- Go
- Goanna
- GoF
- Going gold
- Golang
- Gold-plating
- Golden mean
- Golden ratio
- Golden section
- Goodhart’s Law
- Google Chrome
- Google Cloud Platform
- Google Developer Expert
- Google Fuchsia
- Google Lighthouse
- Google QUIC
- Google TalkBack
- Google Web Server
- Gopher
- GPL
- GPU
- gQUIC
- Graceful Degradation
- Grafana
- Grapheme
- Graphic
- Graphical user interface
- Graphics Interchange Format
- Graphics Processing Unit
- GraphQL
- GRASP
- Greasemonkey
- Greeking
- Greenfield project
- GreenSock
- GreenSock Animation Platform
- Grid
- Grid computing
- Grid track
- Groovy
- GSAP
- gTLD
- Guerrilla patching
- Guetzli
- GUI
- GUID
- gulp
- gulp.js
- Gutter
- GWS
- Gzip
- HA
- Hackathon
- Hacker
- HAML
- Hamming distance
- Handlebars
- HAR
- Hard reset
- Hardware random number generator
- Hardware security module
- Hash
- Hash function
- Hash table
- Hash-based message authentication code
- Hashbang
- Hashtag
- hasLayout
- HATEOAS
- HCI
- HDD
- Head-of-line blocking
- Heading content
- Headless
- Health check
- Heap
- HECVAT
- HEIC
- HEIF
- Helper class
- Heterogenous migration
- Hex
- Hex triplet
- Hexadecimal
- Hick-Hyman Law
- Hick’s Law
- Hidden Web
- High availability
- High Efficiency Image Coding
- High Efficiency Image File Format
- Higher Education Community Vendor Assessment Tool
- Higher-order component
- Higher-order function
- HIP
- Hit
- HITS
- HMAC
- HMAC-based one-time password
- HMR
- HOC
- Hoisting
- HOL blocking
- Holey
- Home page
- Home Page Reader
- Home screen
- Homepage
- HomeSite
- Homogenous migration
- Hooking
- Hop limit
- Horizontal scaling
- Host
- Host Identity Protocol
- Hostname
- Hot data
- Hot linking
- Hot Module Replacement
- HOTP
- Hotwire
- Houdini
- HPR
- HRNG
- HSL
- HSM
- HSTS
- HSV
- HTML
- HTML Abstraction Markup Language
- HTML over the wire
- HTML template
- HTML-in-JS
- HTML/CSS framework
- HTML5
- HTML5 Boilerplate
- HTML 5
- htmx
- HTTP
- HTTP Archive
- HTTP flood attack
- HTTP method
- HTTP request method
- HTTP status code
- HTTP Strict Transport Security
- HTTP verb
- HTTP/2
- HTTP/3
- httpd.conf
- HTTPS
- HTTPS Everywhere
- HubDB
- HubL
- HubSpot Markup Language
- Hue, saturation, lightness
- Hue, saturation, value
- Hugo
- humans.txt
- Human–computer interaction
- Hungarian notation
- Hydration
- Hype cycle
- Hyperlink
- Hyperlink-Induced Topic Search
- Hypermedia as the Engine of Application State
- Hypertext
- HyperText Markup Language
- Hypertext Preprocessor
- Hypertext Transfer Protocol
- Hypertext Transfer Protocol Secure
- Hypervisor
- Hyphenation
- Hypothesis-driven development
- I/O
- I18N
- IA
- IaaS
- IAB
- IaC
- IANA
- IBM Home Page Reader
- IBM WebExplorer
- ICANN
- ICMP
- Icon
- Icon font
- ICT
- ID
- ID selector
- IDE
- Idempotence
- Identifier
- Identity provider
- IDL
- IDP
- IE
- IEEE
- IEO
- IETF
- if
- Iframe
- IIFE
- IIS
- Image
- Image map
- Image replacement
- IMAP
- IME
- Immediate mode
- Immediately Invoked Function Expression
- Immutable
- Import map
- IMS
- In-app browser
- Incident management
- Incident response
- Inclusive design
- Increment
- Incremental Static Regeneration
- Index node
- Indexed color
- Indexed Database
- IndexedDB
- Indexing
- IndieWeb
- Industrial design
- Infinite loop
- Infinite scrolling
- Information and communications technology
- Information architecture
- Information design
- Information foraging
- Information overload
- Information retrieval
- Information scent
- Information Security
- Information security management system
- Information security operations center
- Information technology
- Information technology service management
- Infosec
- Infoset
- Infrastructure as a service
- Infrastructure as Code
- Inheritance
- Initiative for Open Authentication
- Inline
- Inline box
- Inline element
- Inline flow
- Inline formatting context
- Inline linking
- Inline replying
- Inline-level box
- Inline-level element
- Inlinification
- innerHTML
- Inode
- INP
- Input method
- Input method editor
- Input/Output
- Input/output operations per second
- Insertion mode
- Instance store
- Instance variable
- Instant Articles
- Institute of Electrical and Electronics Engineers
- Instrument flight
- Integer
- Integrated development environment
- Intellectual property
- IntelliJ IDEA
- Intent log
- Intent to Implement
- Intent to Prototype
- Interaction design
- Interaction Design Association
- Interaction to Next Paint
- Interactive Advertising Bureau
- Interactive content
- Interactive Data Language
- Interface
- Interface definition language
- Interface description language
- Interface Segregation Principle
- Interleaved posting
- Internal
- International Organization for Standardization
- International Telecommunication Union
- Internationalization
- Internationalized Resource Identifier
- Internet
- Internet Architecture Board
- Internet Archive
- Internet Assigned Numbers Authority
- Internet Control Message Protocol
- Internet Corporation for Assigned Names and Numbers
- Internet Engineering Task Force
- Internet Explorer
- Internet Information Services
- Internet Message Access Protocol
- Internet Protocol
- Internet Protocol Security
- Internet Relay Chat
- Internet Resource Locator
- Internet Server Application Programming Interface
- Internet service provider
- Internet Society
- Internet Universality
- Internet Universality Indicator
- Internet2
- InternetWorks
- InterNIC
- Interoperability
- InterPlanetary File System
- Interpolation
- Interpolation search
- Intersection Observer
- Interstitial
- Intranet
- Intrinsic size
- Intrinsic typography
- Intrinsic web design
- Inversion of Control
- Inverted Triangle CSS
- IoC
- IOPS
- iOS
- IP
- IP address
- IP Multimedia Core Network Subsystem
- IP Multimedia Subsystem
- IP telephony
- IPFS
- IPsec
- IPSECKEY
- iptables
- IPv4
- IPv6
- IRC
- IRI
- IRL
- ISAPI
- Islands architecture
- ISMS
- ISO
- ISO/IEC 27000 series
- ISOC
- ISO 27000
- ISP
- ISR
- IT
- ITCSS
- ITSM
- ITU
- IUI
- IWD
- IxD
- IxDA
- Jakob’s Law
- Jamstack
- Jank
- JAR
- Jasmine
- Java
- Java applet
- Java archive
- Java Database Connectivity
- Java Development Kit
- Java servlet
- Java virtual machine
- JavaFX
- JavaScript
- JavaScript framework
- JavaScript library
- JavaScript Object Notation
- JavaScript Object Notation for Linked Data
- JavaScript Style Sheets
- JavaScript Syntax Extension
- JavaScript XML
- JavaServer Pages
- JAWS
- JDBC
- JDK
- Jekyll
- Jenkins
- Jetty
- Jimdo
- Jinja
- Jinjava
- Jira
- JIT
- JIT compiler
- Job Access With Speech
- Joint Photographic Experts Group
- Joomla
- JPEG
- JPG
- jQuery
- JS
- JScript
- JSLint
- JSON
- JSON Feed
- JSON Web Encryption
- JSON Web Signature
- JSON Web Token
- JSON with Padding
- JSON-LD
- JSON-P
- JSON5
- JSON5 Data Interchange Format
- JSONP
- JSP
- JSS
- JSSS
- JSX
- Just in Time
- Just-in-time compilation
- JVM
- JWS
- JWT
- K-Meleon
- K8s
- Kanban
- Karp–Rabin algorithm
- Kebab case
- Keeping the lights on
- Kerberos
- Kerning
- Key
- KEY
- Key frame
- Key management
- Key performance indicator
- Keyframe
- Keyword
- Key–value database
- KHTML
- Kibana
- KMP algorithm
- Knowledge Graph
- Knuth–Morris–Pratt algorithm
- Konqueror
- KPI
- KTLO
- Kubernetes
- L10N
- Lambda abstraction
- Lambda expression
- LAMP
- LAN
- Landing page
- Language
- Language metadata
- Language subtag
- Language tag
- Laravel
- Large viewport
- Large-Scale Scrum
- Largest Contentful Paint
- Last Call Working Draft
- Last in, first out
- Latency
- Latent semantic indexing
- LaTeX
- Launch
- Law of Conservation of Complexity
- Law of Demeter
- Law of Leaky Abstractions
- Layout
- Layout engine
- Layout table
- Lazy loading
- LCP
- LCU
- LCWD
- LDAP
- Lead time
- Leading
- Leaky abstraction
- Lean
- Leaner Style Sheets
- Left-to-right
- Legibility
- Lerna
- LeSS
- Less
- LeSS Huge
- Letter spacing
- Let’s Encrypt
- Level of effort
- Levenshtein distance
- Lexical scope
- Library
- Library World Wide Web
- libwww
- LIFO
- Lift and shift
- Ligature
- Light mode
- Lighthouse
- Lightweight Directory Access Protocol
- Lightweight markup language
- Likert scale
- Limited-quirks mode
- Line box
- Line ending
- Line feed
- Line spacing
- Line terminator
- Linear responsibility chart
- Linearizability
- Lines of code
- Link
- Link equity
- Link farm
- Link juice
- Link rot
- Linked Data
- Linked list
- Linter
- Linting
- Linux
- Linux Standard Base
- Linux, Apache, MySQL, PHP/Perl/Python
- Liquid
- LIS
- Liskov Substitution Principle
- Lisp
- Lit
- Lite Mode
- LitElement
- Literal
- Little’s Law
- LMGTFY
- LML
- Load balancer
- Load Balancer Capacity Unit
- Load balancing
- Load time
- LOC
- Local
- Local area network
- Local scope
- Local storage
- Local variable
- Local-part
- Locale
- localhost
- Localization
- Location information server
- Lock file
- Lock file poisoning
- Lockfile
- LOE
- Log file
- Logging
- Logical properties
- Login
- Logon
- Long task
- Long-Term Support
- longdesc
- Longest common substring
- Look and feel
- Loop
- Lorem ipsum
- Lossless
- Lossy
- Love-at-first-sight pattern
- Low vision
- LRC
- LSB
- LSI
- LSP
- LTR
- LTS
- Lynx
- MAC
- MAC address
- Mac OS
- Machine learning
- macOS
- macOS, Apache, MySQL, PHP/Perl/Python
- Macromedia Flash
- MacWWW
- Magic code
- Magic cookie
- Mailjet Markup Language
- Main thread
- Maintainability
- Maintenance
- Makefile
- MAM
- MAMP
- Man-in-the-middle attack
- Manifesto for Agile Software Development
- Margin
- Margin collapsing
- Markdown
- Marketing
- Markup
- Markup language
- Massively parallel processing
- Masthead
- Material Design
- Mathematical Markup Language
- Mathematical markup language
- MathML
- MAU
- Maven
- Maximum segment sum problem
- Maximum subarray problem
- McCabe score
- MD
- MD2
- MD4
- MD5
- MD6
- MDL
- MDN
- MDN Web Docs
- MDX
- MEAN
- Media
- Media access control address
- Media asset management
- Media query
- Media type
- Medium integer
- Meet-in-the-middle attack
- Mega menu
- Memoization
- Menu
- Merge queue
- Merge request
- Merging
- Message authentication code
- Message Digest
- Meta element
- Meta programming
- Metadata
- Metadata content
- Metaprogramming
- Meteor
- Method
- Method overloading
- Method stub
- Metro
- MFA
- MHTML
- Microformat
- Microservice
- Microservice architecture
- Microsite
- Microsoft Active Accessibility
- Microsoft Design Language
- Microsoft Edge
- Microsoft FrontPage
- Microsoft Narrator
- Microsoft Silverlight
- Microsoft Windows
- Microtask
- Middleware
- Millennium bug
- MIMD
- MIME
- MIME encapsulation of aggregate HTML documents
- MIME sniffing
- MIME type
- Mini Program
- Minification
- Minifier
- Minimum spanning tree
- Minimum viable product
- Minimum weight spanning tree
- MIP
- Mipmap
- MISD
- MITM
- Mixin
- MJML
- ML
- Mobile
- Mobile First
- Mobile Instant Pages
- Mobilegeddon
- Mocha
- Mock object
- Mocking
- Modal
- Model–View–Controller
- Model–View–Viewmodel
- Modernizr
- Modular design
- Module
- Monitor
- Monitoring
- Monkey patching
- Monolith
- Monolithic application
- Monorepo
- monospace
- Monthly Active Users
- Mosaic
- Mouse grid
- Moving Picture Experts Group
- Mozilla Developer Center
- Mozilla Developer Network
- Mozilla Firefox
- MPA
- MPEG
- MPP
- MR
- MSA
- MSAA
- MSHTML
- MSIE
- MST
- mTLS
- Multi-factor authentication
- Multi-page application
- Multimedia
- Multiple inheritance
- Multiple instruction, multiple data
- Multiple instruction, single data
- Multiprocessing
- Multipurpose Internet Mail Extensions
- Multithreading
- Muphry’s Law
- Murphy’s Law
- Mustache
- Mutable
- Mutation
- Mutual authentication
- Mutual TLS authentication
- MVC
- MVP
- MVVM
- MX
- MySQL
- n-based indexing
- NACK
- NACL
- NAK
- Naked type
- Name binding
- Name server
- Namespace
- NaN
- Narrator
- NAT
- National Institute of Standards and Technology
- Native
- NativeScript
- Natural interface
- Natural key
- Natural user interface
- Navigation
- Navigator
- NCSA Common Log Format
- NDA
- Necro-posting
- Negative space
- Nesting
- Net Promoter Score
- Netscape Communicator
- Netscape Navigator
- Netscape 4
- Network
- Network address translation
- Network Information Center
- Network Mapper
- Network packet
- Neutral character
- Newbie
- Newline
- News aggregator
- Next.js
- Nexus
- NFR
- NGINX
- Night mode
- Ninety–Ninety Rule
- NIST
- Nmap
- No-quirks mode
- Node
- Node Package Manager
- Node.js
- Noflake Manifesto
- nofollow
- Nolan’s Law
- Non-disclosure agreement
- Non-functional requirement
- Non-relational database
- Non-replaced element
- Non-Zero Rule
- Non-Zero Winding Rule
- Nonce
- NonNullable
- NonVisual Desktop Access
- Noob
- Normal form
- Normalization
- Normalize.css
- Normative
- North star metric
- NoSQL
- Not a Number
- Notification system
- Now page
- npm
- NPS
- NS
- NSM
- NUI
- Null
- Null device
- Null pointer
- Number
- Number sign
- Numeral
- Numeric character reference
- Numeric up/down
- Numerical digit
- Nuxt.js
- NVDA
- OAEP
- OATH
- OAuth
- Obfuscation
- Obfuscript
- Object
- Object-code compatibility
- Object-Oriented CSS
- Object-oriented programming
- Objectives and key results
- Objectives, goals, strategies, and measures
- Observer
- Observer pattern
- OCP
- OCSP
- OCSP stapling
- Offline
- Offline First
- OGP
- OGSM
- OIDC
- OKR
- OLA
- OLAP
- OLTP
- Omnichannel
- On-prem
- On-premises software
- One-based indexing
- One-time password
- Onion Router
- Online analytical processing
- Online Certificate Status Protocol
- Online transaction processing
- Ontology
- OOCSS
- OOM
- OOP
- OOPIF
- Open Authorization
- Open Graph
- Open Graph Protocol
- Open Group Architecture Framework
- Open Source
- Open Systems Interconnection model
- Open Web Application Security Project
- Open Web Docs
- OpenAPI
- OpenAPI Specification
- OpenID
- OpenID Connect
- OpenType
- Open–Closed Principle
- Opera
- Opera Mini
- Operand
- Operating system
- Operating-level agreement
- Operational-level agreement
- Operations-level agreement
- Operator
- OPFS
- Optimal Asymmetric Encryption Padding
- Optimization
- Optional markup
- Orca
- Organizational-level agreement
- Origin
- Origin Private File System
- Origin trials
- Orphan
- Orthogonality
- OS
- OSI model
- OTA
- OTF
- OTP
- Out of memory
- Out-of-process iframe
- Outline
- Over the air
- Over-testing
- OWASP
- OWD
- OWL
- PaaS
- Package
- Package manager
- package-lock.json
- package.json
- Packaged Offline/Online Webpage
- Packed
- Packet
- Padding
- Padding oracle attack
- Page
- Page impression
- Page parking
- Page prediction
- Page Quality
- Page view
- PageRank
- PageSpeed
- Painless
- Paint
- Pair programming
- Palpable content
- PANOSE
- Paper prototyping
- Paradigm
- Parallax scrolling
- Parallel browsing
- Parameter
- Paraphrase testing
- Parcel
- Pareto Principle
- Pareto Rule
- Parkinson’s Law
- Parse error
- Parsed character data
- Parser
- Parsing
- Partial exact-match domain
- Partytown
- Pascal case
- Pass the Cookie attack
- Passkey
- Patch
- PATH
- Path
- Pattern
- Pattern library
- Pave the Cowpaths
- Pay-per-click
- Payload
- Payment Card Industry Data Security Standard
- Paywall
- PBI
- PCDATA
- PCI DSS
- Peer review
- PEMD
- Pen test
- Penetration testing
- Pentest
- Perceivable, operable, understandable, robust
- Perceived performance
- Percent encoding
- Performance
- Performance budget
- Performance indicator
- Perl
- Permalink
- Persona
- Personal data
- Personal Home Page
- Personally identifiable information
- Peter Principle
- PFS
- PhantomJS
- Phishing
- Phoenix
- Phoenix server pattern
- Photoshop
- PHP
- PhpStorm
- Phrasing content
- PI
- PII
- Pinball pattern
- Ping
- Pinging
- pip
- Pixel
- Pixel tag
- Pixel-perfect
- PKCS
- PKI
- Placeholder
- Placeholder text
- Plain-text
- Plane
- Platform as a service
- Platform evangelism
- Platform modernization
- Playback attack
- Plugin
- Plus-minus testing
- Plusignment
- PMA
- PNG
- pnpm
- POC
- Pod
- Point of presence
- Pointer
- Pointing device
- POLA
- Policy pattern
- POLP
- Polyfill
- Polymer Project
- POM
- POMP
- POP
- Pop-over
- Pop-under
- Pop-up
- Port
- Port number
- Portable code
- Portable Document Format
- Portable Network Graphics
- Portal
- Post mortem
- Post mortem analysis
- Post Office Protocol
- PostCSS
- Postel’s Law
- POUR
- POV
- POW
- PowerShell
- PPC
- PQ
- PR
- Pre-production environment
- Preact
- Predication
- Preferred style sheet
- Prefetching
- Premature optimization
- Prerendering
- Presentation
- Presentation MathML
- Presto
- Primary key
- Primitive
- Princeton architecture
- Principal
- Principal box
- Principle of Least Astonishment
- Principle of Least Authority
- Principle of Least Knowledge
- Principle of Least Privilege
- Principle of Least Surprise
- Principle of Minimal Privilege
- Print style sheet
- Priority queue
- Privacy
- Privacy Sandbox
- Privilege escalation
- PRNG
- Proactive monitoring
- Processing instruction
- Product backlog
- Product backlog item
- Product owner
- Production
- Production environment
- Program stack
- Programmer
- Programming
- Programming language
- Progressive Enhancement
- Progressive font enrichment
- Progressive rendering
- Progressive web app
- Project Object Model
- Prometheus
- Promise
- Prompt injection attack
- Proof of concept
- Proof of principle
- Proof of value
- Prop
- Prop drilling
- Property
- Protocol
- Prototype
- Prototype chain
- Prototype pattern
- Prototype pollution attack
- Prototyping
- Proxy
- Proxy server
- PRPL
- Pseudo-class
- Pseudo-code
- Pseudo-element
- Pseudo-random number generator
- PSON
- PTR
- Public Key Cryptography Standards
- Public key infrastructure
- Pull request
- Punycode
- Puppet
- Puppeteer
- Push notification
- Push technology
- Push, render, pre-cache, lazy-load
- PV
- PWA
- Python
- QA
- QC
- qem
- qooxdoo
- QPS
- QRNG
- Quality
- Quality assistance
- Quality assurance
- Quality control
- Quantity query
- Quantum random number generator
- Queries per second
- Query
- Query language
- QUIC
- Quick UDP Internet Connections
- Quirks mode
- RAB
- Rabin–Karp algorithm
- Race condition
- Race hazard
- RACI matrix
- RAD
- RADIUS
- Rails
- Raku
- RAM
- Random number generation
- Random number generator
- Random variable
- Random-access memory
- Ranking
- Rapid application building
- Rapid application development
- Rapid prototyping
- Raster image
- Rate limiting
- Rax
- RBAC
- RCA
- RCDATA
- RCE
- RCS
- RDBMS
- RDF
- RDF Schema
- RDF Site Summary
- RDF-S
- RDFS
- RDP
- RDSMS
- React
- React Native
- Reactive Extensions for JavaScript
- Reactive Manifesto
- Reactive programming
- ReactJS
- Read the fucking manual
- Readability
- Reading disorder
- README
- Read–Eval–Print Loop
- Real user monitoring
- RealAudio
- Really Simple Syndication
- RealVideo
- Recidivism
- Recommendation
- Record of intent
- Recovery point objective
- Recovery time objective
- Recursion
- Recursive hashing
- Red, green, and blue
- Redesign
- Redirect
- Redirect chain
- Redundancy
- Redux
- Reed–Solomon codes
- Refactoring
- Reference error
- Reference pixel
- Referential opacity
- Referential transparency
- Referer
- Referrer
- Reflow
- Regex
- Registrar
- Regular expression
- Rehosting
- Rehydration
- Relational data stream management system
- Relational database
- Relational database management system
- Relational model
- Relative sizing
- Relaunch
- Release to Manufacturing
- Release to the Web
- Release train
- Rem
- Remix
- Remote Authentication Dial-In User Service
- Remote code execution
- Remote Desktop Protocol
- Remote method invocation
- Remote procedure call
- Render tree
- Renderer
- Rendering
- Rendering engine
- RenderingNG
- REP
- Repeated-measures design
- REPL
- Replaceable character data
- Replaced element
- Replay attack
- Repo
- Repository
- Representational State Transfer
- Request
- Request for Comments
- Request header
- Request method
- Request-time render
- Requests per second
- RequireJS
- Reset
- Reset style sheet
- Resolution
- Resource Description Framework
- Resource Hints
- Resource record
- Response
- Response header
- Responsibility assignment matrix
- Responsive design
- Responsive Images Community Group
- Responsive Issues Community Group
- Responsive web design
- Responsiveness
- REST
- Restricted production
- Retained mode
- Revalidation
- Reverse proxy
- Revision control
- Revision control system
- RFC
- RGB
- RIA
- RIB
- RICG
- Rich Communication Services
- Rich Internet application
- Rich Site Summary
- Rich Text Format
- Rich web application
- Right-to-left
- Rights, openness, accessibility, multi-stakeholder participation, cross-cutting issues
- Rijndael
- RIRO
- RMI
- RNG
- Roadmap
- ROAM
- ROAM-X
- Robot
- Robots Exclusion Protocol
- Robots exclusion standard
- robots.txt
- Robustness Principle
- Role-based access control
- Role-based security
- Rolling checksum
- Rolling hash
- Root
- Root cause analysis
- Root directory
- Root element
- Root em
- Root name server
- Root node
- Root server
- Root zone
- Rooting
- Round-Trip Delay Time
- Round-Trip Time
- Route
- Route 53
- Router
- Routine
- Routing
- Routing information base
- Routing table
- RPC
- RPM
- RPM Package Manager
- RPO
- RPS
- RR
- RSS
- RTD
- RTF
- RTFM
- RTL
- RTM
- RTO
- RTR
- RTT
- RTW
- Rubber ducking
- Rubbish in, rubbish out
- Ruby
- Ruby on Rails
- RubyGems
- Rule
- Rule set
- RUM
- Runbook
- Runtime
- Runtime compilation
- Runtime environment
- Runtime stack
- Runtime system
- RWD
- RxJS
- S-expression
- S3
- SaaS
- Safari
- SAFe
- SAK
- Samba
- Same origin
- Same-origin policy
- SAML
- SAN
- Sandbox
- sans-serif
- SAP User Interface for HTML5
- SAPUI5
- Sass
- SassScript
- SAST
- SBML
- Scalable and Modular Architecture for CSS
- Scalable Vector Graphics
- Scalar
- Scaled Agile Framework
- Scaled Scrum
- Schema stitching
- SCM
- Scope
- Scoped styles
- Screen magnifier
- Screen reader
- Script
- Scripting language
- Scroll Snap
- Scrolling
- Scrollport
- Scrum
- Scrum master
- Scrum of Scrums
- Scrum team
- Scrum values
- SCSS
- SDE
- SDK
- SDLC
- SDP
- SEA
- SeaMonkey
- Search engine advertising
- Search engine indexing
- Search engine marketing
- Search engine optimization
- Search engine results page
- Searching
- Second normal form
- Second Rule of ARIA
- Section 508
- Sectioning content
- Secure context
- Secure Shell
- Secure Sockets Layer
- Security
- Security Assertion Markup Language
- Security hacker
- Security operations center
- Security principal
- Security token
- security.txt
- Segregation of duties
- Selector
- Selenium
- Self-contained action
- SEM
- Semantic Versioning
- Semantic Web
- Semantically Interlinked Online Communities
- Semantics
- SemVer
- Sender Policy Framework
- SEO
- Separation of Concerns
- Separation of duties
- Serializability
- Serialization
- Serialization agreement
- Serif
- serif
- SERP
- Server
- Server cluster
- Server farm
- Server logs
- Server Name Indication
- Server push
- Server side
- Server-side rendering
- Serverless computing
- Service discovery
- Service discovery protocol
- Service level agreement
- Service level expectation
- Service level indicator
- Service level objective
- Service Statelessness Principle
- Service worker
- Service-oriented architecture
- Servlet
- Session
- Session affinity
- Session hijacking
- Session storage
- Set
- sexp
- SFTP
- SGML
- Shadow DOM
- Shadow host
- Shadow IT
- Shadow root
- Shadow tree
- Shape Up
- Shard
- Sharding
- Shared hosting
- Shared tenancy
- Shared worker
- Shebang
- Shell
- Shim
- Shockwave Flash
- Shopping cart
- Shortcut icon
- Shorthand
- SI
- Siamese twins document
- SIG
- SIGHUP
- Sign-in
- Sign-on
- Signed HTTP Exchanges
- Silk
- Silverlight
- SIMD
- Simple Knowledge Organization System
- Simple Mail Transfer Protocol
- Simple Object Access Protocol
- Single instruction, multiple data
- Single instruction, single data
- Single point of failure
- Single Responsibility Principle
- Single-page application
- Single-serving site
- Singularity
- SIOC
- SISD
- Site
- Site isolation
- Site map
- Sitemaps
- Skeleton screen
- Sketch
- Skia
- Skin
- Skip navigation
- SKOS
- SLA
- SLE
- SLI
- Sliding Doors
- SLO
- SLOC
- Sloppy mode
- Slot
- Slowloris
- Slug
- SMACSS
- Small integer
- Small viewport
- Smalltalk
- Smashing Magazine
- SME
- Smi
- SMIL
- Smishing
- Smoke testing
- SMTP
- Snake case
- Snap position
- SNI
- Snowflake server
- Snowpack
- SOA
- SOAP
- SOC
- Social Linked Data
- Social Web
- SOD
- Soft launch
- Soft opening
- Software
- Software as a service
- Software crisis
- Software developer
- Software development
- Software development engineer
- Software development environment
- Software development kit
- Software development lifecycle
- Software engineer
- Software framework
- Software modernization
- Software release train
- Software stack
- Software testing
- SOLID
- Solid
- Solid project
- Solid Protocol
- Solution stack
- SOP
- Sorting
- Source code compatibility
- Source code management
- Source compatibility
- Source control management
- Source lines of code
- Source map
- SPA
- Spacer
- Space–time tradeoff
- Spaghetti code
- Spam
- Spamdexing
- Spamming
- Spatial anti-aliasing
- SPDY
- Spec
- Specification
- Specificity
- Spectre
- Speech synthesis
- Speed Index
- Speed of service
- SPF
- Spider
- Spider trap
- Spike
- Spinner
- Splash screen
- SPOF
- Spoofing
- Spread
- Sprint
- Sprint goal
- Sprite
- SQL
- SQL injection
- SQLite
- SQS
- Squad
- Squarespace
- Squint test
- src
- sRGB
- SRI
- SRP
- SRV
- SSG
- SSH
- SSH File Transfer Protocol
- SSIM
- SSL
- SSR
- SSS
- Stack
- Stack frame
- Stack level
- Stack Overflow
- Stacking context
- Staging
- Staging environment
- Stand-up
- Standard
- Standard Generalized Markup Language
- standard Red Green Blue
- Standards mode
- Standby redundancy
- Star
- Star hack
- Start of authority
- Start page
- Start tag
- State
- State management
- Statement
- Statement coverage
- Static application security testing
- Static scope
- Static site generation
- Static site generator
- Static website
- Status code
- STFW
- Sticky session
- Stimulus
- Storage
- Storage area network
- Storage engine
- Storybook
- STP
- Strada
- Strategy pattern
- Stream
- Streaming media
- Strict mode
- String
- String interpolation
- Strong character
- Structural similarity index measure
- Structure
- Structured data
- Structured data entity
- Structured Query Language
- Stub
- Style guide
- Style query
- Style rule
- Style sheet
- Styled component
- styled-components
- stylelint
- Styling
- Stylus
- Subject Alternative Name
- Subject-matter expert
- Submodule
- Subnav
- Subnavigation
- Subnet
- Subnet mask
- Subnetwork
- Subpixel rendering
- Subresource Integrity
- Subroutine
- Subsetting
- Subversion
- SUIT CSS
- Superkey
- Superuser
- Supply chain attack
- Support
- Surface Web
- Surfing
- Surrogate key
- SVG
- SVN
- Swagger
- Swagger Specification
- Switchover
- SXG
- Symbol
- Symbolic expression
- Symbolication
- Symfony
- SYN
- Synchronized Multimedia Integration Language
- Synchronizer token pattern
- Synchronous
- Syndication
- Syntactic sugar
- Syntax
- Syntax analysis
- Synthetic monitoring
- syslog
- Systems Biology Markup Language
- T3 stack
- Tab
- Tab icon
- Tabbed document interface
- Table box
- Table formatting context
- Tabnabbing
- Tabular data
- Tachyons
- TAG
- Tag
- Tag management system
- Tag soup
- Tagging
- Tail call
- Tail call elimination
- Tail call optimization
- Tailoring
- Tailwind
- Tailwind CSS
- TalkBack
- tar
- Tarball
- TBT
- Tcl
- TCO
- TCP
- TDD
- TDI
- TDZ
- Tech lead
- Tech stack
- Tech Twitter
- Technical and organizational measure
- Technical Architecture Group
- Technical debt
- Technical key
- Technical lead
- Technical program manager
- Technical standard
- Technological protection measures
- Technological singularity
- Technology debt
- Telnet
- Template
- Template engine
- Template language
- Template literals
- Template processor
- Template strings
- Template system
- Templating language
- Temporal dead zone
- Temporary storage
- Ten-Second Rule
- Terminal
- Ternary operator
- Tesler’s Law
- Test coverage
- Test pyramid
- Test-driven development
- Testing
- TeX
- Text-based web browser
- Text-to-speech
- Textile
- The Million Dollar Homepage
- The Noflake Manifesto
- The Onion Router
- The Open Group Architecture Framework
- Theme
- Third normal form
- Third party
- Third Rule of ARIA
- this
- Thread
- Three-Click Rule
- TIL
- Time box
- Time series database
- Time to First Byte
- Time to Interactive
- Time to Live
- Time-based one-time password
- Timed text
- Timestamp
- Time–memory tradeoff
- Timing attack
- tink
- Tiny integer
- Tizen
- TL
- TLB
- TLD
- TLS
- TLS Certificate Status Request extension
- TM
- TMS
- TMTO
- To-do
- Toast
- Todo
- TOFU
- TOGAF
- Token
- Token authentication
- Tokenization
- TOM
- Tomcat
- TOML
- Tom’s Obvious, Minimal Language
- Tooling
- Top-level domain
- Top-posting
- TOP500
- Top–down design
- Tor
- Tor Browser
- Tor network
- Tor Project
- Total Blocking Time
- Total productive maintenance
- Total quality management
- TOTP
- TPM
- TPS
- TQM
- Tracer code
- Tracing
- Tracking
- Tracking pixel
- Trade
- Traffic spike
- Transactions per second
- Transclusion
- Transcompiler
- Transcreation
- Transcript
- Transitional app
- Translation lookaside buffer
- Translation management system
- Translation memory
- Transmission Control Protocol
- Transpiler
- Transport Layer Security
- Travis CI
- Tree
- Tree shaking
- Tree traversal
- Triadic colors
- Trident
- Trie
- TRNG
- Truck factor
- True random number generator
- TrueDoc
- TrueType
- Trunk-based development
- Trust on first use
- Trust upon first use
- Trusted Types
- TrustRank
- try
- try…catch
- TSDB
- TTF
- TTFB
- TTI
- TTL
- TTS
- TUFU
- Turbo
- Turbo mode
- Turbo pages
- Turing completeness
- Two-factor authentication
- TXT
- Type
- Type assertion
- Type casting
- Type coercion
- Type conversion
- Type design
- Type grinding
- Type I error
- Type II error
- Type juggling
- Type predicate
- Type predicate function
- Type selector
- Type system
- Typeface
- TypeScript
- TYPO3
- Typography
- Typosquatting
- Typosquatting attack
- UA
- UA string
- UAAG
- UAT
- UBA
- UBE
- UCD
- UCS
- UDD
- UDJO
- UDP
- UDP flood attack
- UGC
- Uglification
- UI
- UI framework
- UI redressing
- UIML
- UKM
- UMD
- UML
- undefined
- Underscore hack
- Unicode
- Unicode Bidirectional Algorithm
- Unicode Consortium
- Unicode standard
- Unified Modeling Language
- Uniform Resource Characteristic
- Uniform Resource Identifier
- Uniform Resource Locator
- Uniform Resource Name
- Uninitialized pointer
- Uninitialized variable
- Union type
- Unique selling point
- Unique selling proposition
- Unique value proposition
- Unit testing
- Universal Access
- Universal Coded Character Set
- Universal cross-site scripting
- Universal design
- Universal Module Definition
- Universal selector
- Universal XSS
- Universally unique identifier
- Uniwidth typeface
- Unix
- Unix philosophy
- Unix time
- Unsolicited bulk email
- Unstoppable domain
- UPA
- Upsert
- Upstream
- URC
- Urchin Tracking Module
- URI
- URL
- URL encoding
- URL forwarding
- URL redirection
- URL slug
- URL-keyed metrics
- URN
- US-ASCII
- Usability
- Usability inspection
- Usability Professionals Association
- Usability testing
- Usenet
- User
- User acceptance testing
- User agent
- User Agent Accessibility Guidelines
- User agent sniffing
- User agent string
- User Datagram Protocol
- User experience
- User Experience Professionals Association
- User interface
- User interface markup language
- User JavaScript
- User story
- User testing
- User-centered design
- User-driven development
- User-generated content
- Userscript
- Uses page
- Using declarations just once
- USP
- UTC
- UTC offset
- UTF-16
- UTF-32
- UTF-8
- Utility class
- UTM
- UUID
- UVP
- UX
- UXPA
- UXSS
- Validation
- Validator
- Value
- Value-driven design
- Variable
- Variable expansion
- Variable font
- Variable interpolation
- Variable scope
- Variable substitution
- Variable-length quantity
- Variable-length subnet mask
- VBA
- VDD
- Vector image
- Velocity
- Vendor prefix
- Verification
- Version control
- Versioning
- Vertical scaling
- vi
- Viewport
- Vim
- Virtual inheritance
- Virtual LAN
- Virtual machine
- Virtual machine manager
- Virtual machine monitor
- Virtual mode
- Virtual private cloud
- Virtual private network
- Virtual reality
- Virtualization
- Virtualizer
- Vishing
- Visual Basic for Applications
- Visual formatting model
- Visual impairment
- Visual regression testing
- Visual Studio Code
- Vite
- VLAN
- VLQ
- VLSM
- VM
- VMM
- Voice over IP
- Voice phishing
- Voice user interface
- VoiceOver
- VoiceXML
- Void element
- VoIP
- Voluntary Product Accessibility Template
- von Neumann architecture
- von Neumann model
- VPAT
- VPC
- VPN
- VR
- VRT
- VS Code
- Vue
- Vue.js
- VuePress
- Vuex
- VUI
- W3C
- WAF
- WAI
- WAI-ARIA
- Walking the tree
- WAMP
- WAN
- WAP
- WAR
- Wasm
- WaSP
- WAT
- Waterfall
- WAU
- WCAG
- WCAG Samurai
- WCM
- WCMS
- Weak character
- Weak code ownership
- Web Accessibility Initiative
- Web address
- Web Almanac
- Web analytics
- Web app
- Web application
- Web application archive
- Web application firewall
- Web application framework
- Web beacon
- Web browser
- Web bug
- Web Bundles
- Web cache
- Web component
- Web content
- Web Content Accessibility Guidelines
- Web content management system
- Web design
- Web development
- Web Distributed Authoring and Versioning
- Web feed
- Web font
- Web forms
- Web framework
- Web Graphics Library
- Web Hypertext Application Technology Working Group
- Web IDL
- Web Incubator Community Group
- Web indexing
- Web Ontology Language
- Web Open Font Format
- Web Packaging
- Web page
- Web performance
- Web performance optimization
- Web platform
- Web Platform Baseline
- Web Platform Incubator Community Group
- Web Real-Time Communication
- Web resource
- Web service
- Web service application programming interface
- Web site
- Web standard
- Web standards movement
- Web Standards Project
- Web storage
- Web tracking
- Web traffic
- Web typography
- Web Video Text Tracks
- Web Vitals
- Web worker
- Web-Interoperable Runtimes Community Group
- Web3
- Webalizer
- WebAssembly
- WebAssembly text format
- WebAuthn
- WebDAV
- WebDriver
- WebDriver BiDi
- WebExplorer
- WebFTP
- WebGL
- Webhook
- WebKit
- Webkrauts
- Weblog
- WebM
- Webmaster
- Webmention
- WebP
- Webpack
- WebPageTest
- WebRTC
- Website
- Website application programming interface
- WebSocket
- WebStorm
- WebView
- WebVTT
- Web 2.0
- Web 3.0
- WeChat Mini Program
- Weebly
- Weekly Active Users
- Weex
- WeiXin Markup Language
- WeiXin Script
- WeiXin Style Sheets
- Well-formedness
- WET
- Wget
- What you see is all you get
- What you see is what you get
- WHATWG
- while
- White-box testing
- Whitelist
- Whitespace
- WHOIS
- WICG
- Wide area network
- Widow
- Wiki
- Window-Eyes
- Windows
- Windows Aero
- Windows, Apache, MySQL, PHP/Perl/Python
- WinterCG
- WIP
- Wireframe
- Wireless Application Protocol
- Wireless Markup Language
- Within-subjects design
- Wix
- WLM
- WML
- Wobbly Transformation Format 8-Bit
- WOFF
- WORA
- WordPress
- WordPress theme
- Work in progress
- Workaround
- Workbox
- Working Draft
- Worklet
- Workload management
- World Wide Web
- World Wide Web Consortium
- WorldWideWeb
- WPO
- Wrapper
- Write once, run anywhere
- writing-mode
- WSAPI
- WTF-8
- WWW
- WXML
- WXS
- WXSS
- WYSIAYG
- WYSIWYG
- x-height
- X.509
- XAML
- XForms
- XHP
- XHR
- XHTML
- XLink
- XML
- XML external entity attack
- XML Information Set
- XML Infoset
- XML Schema Definition
- XML User Interface Language
- XML-RPC
- XMLHttpRequest
- XP
- XPath
- XPointer
- XQuery
- XSD
- XSL
- XSLT
- XSRF
- XSS
- XSSI
- XUL
- XXE attack
- Y2K
- YAGNI
- Yahoo Developer Network
- Yahoo Query Language
- Yahoo User Interface
- Yahoo User Interface Library
- YAML
- YAML Ain’t Markup Language
- Yandex Browser
- Yarn
- yarn.lock
- YDN
- Year 2000 problem
- Yellowdog Updater, Modified
- Yet Another Multicolumn Layout
- yield
- YMYL
- You Aren’t Gonna Need It
- Your Money or Your Life
- YQL
- YSlow
- YUI
- yum
- Z shell
- Zen Coding
- Zero-based indexing
- Zero-configuration networking
- Zero-indexed
- Zeroconf
- Zeus Web Server
- ZIP
- Zombie cookie
- Zone file
- Zone offset
- Zsh
- ZWS