SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/tech-unicode-max-code-point

What is the highest code point Unicode allows?

U+10FFFF, a little over 1.1 million possible code points.

Start playing free

  1. U+FFFF
  2. U+10FFFF ✔
  3. U+FFFFFFFF

Why: Unicode tops out at U+10FFFF so UTF-16 can reach every scalar value. U+FFFF is only the end of the first plane, and many emoji lie above it.

Huh, didn't know that: RFC 3629 warns that software must reject code points above U+10FFFF, or buffer sizing bugs can follow.

The dad joke
Why did Unicode stop at U+10FFFF? It ran out of room on its plane.
Like this card?
Play the game

References

Answer: U+10FFFF. Unicode tops out at U+10FFFF so UTF-16 can reach every scalar value. U+FFFF is only the end of the first plane, and many emoji lie above it.

  1. RFC 3629: UTF-8, a transformation format of ISO 10646 www.rfc-editor.org/rfc/rfc3629.txt
    characters from the U+0000..U+10FFFF range (the UTF-16 accessible range) are encoded using sequences of 1 to 4 octets
    Checked 2026-10-10.

Think this answer is wrong? Tap "Challenge this answer" on the card in the game and tell us why.

Test yourself in the game

Tech & GadgetsIn UTF-8, how many bytes can one Unicode scalar value take?Tech & GadgetsHow many bits does standard ASCII use for each character?Tech & GadgetsA plain ASCII text file is read as UTF-8. What happens?

That's stuff everyone should know.