Unicode Planes

The Unicode standard organizes its full codepoint space (U+0000 through U+10FFFF — over 1.1 million codepoints) into 17 planes of 65,536 codepoints each. Planes are numbered 0 through 16. Most characters in everyday use live in Plane 0, the Basic Multilingual Plane (BMP). Emoji, historic scripts, and CJK extensions occupy the supplementary planes.

The plane a character belongs to affects how it must be encoded. Characters in the BMP fit in a single UTF-16 code unit (2 bytes). Characters in Planes 1–16 require a surrogate pair in UTF-16 (4 bytes) — which is why JavaScript's '🔥'.length === 2 even though it looks like one character.

BMP

Basic Multilingual Plane

64,166
U+0000 – U+FFFF
Plane 0
SMP

Supplementary Multilingual Plane

28,869
U+10000 – U+1FFFF
Plane 1
SIP

Supplementary Ideographic Plane

61,513
U+20000 – U+2FFFF
Plane 2
TIP

Tertiary Ideographic Plane

13,429
U+30000 – U+3FFFF
Plane 3
SSP

Supplementary Special-purpose Plane

337
U+E0000 – U+EFFFF
Plane 14
SPUA-A

Supplementary Private Use Area-A

65,534
U+F0000 – U+FFFFF
Plane 15
SPUA-B

Supplementary Private Use Area-B

65,534
U+100000 – U+10FFFF
Plane 16

Planes 4–13

Planes 4 through 13 (U+40000–U+DFFFF) are currently unassigned. They are reserved for future expansion of the Unicode standard. No characters have been allocated to these planes yet.