Plane · WebGlossary.info

In the Unicode standard, a continuous group of 65,536 (2¹⁶) code points. There are 17 planes, identified by the numbers 0 to 16, which corresponds with the possible values 00–10₁₆ of the first two positions in six-position hexadecimal format (U+hhhhhh). Plane 0 is the Basic Multilingual Plane (BMP), which contains the most commonly used characters. The higher planes 1 through 16 are called supplementary planes. The last code point in Unicode is the last code point in plane 16, U+10FFFF. As of Unicode version 12.1, six of the planes have assigned code points (characters), and four are named. The limit of 17 planes is due to UTF-16, which can encode 2²⁰ code points (16 planes) as pairs of words, plus the BMP as a single word. UTF-8 was designed with a much larger limit of 2³¹ (2,147,483,648) code points (32,768 planes), and can encode 2²¹ (2,097,152) code points (32 planes) even under the current limit of 4 bytes. The 17 planes can accommodate 1,114,112 code points. ← Wikipedia