ASCII 31
ASCII 31 is Unit Separator — the control character US.
Every representation
| Character | US (not printable) |
| Name | Unit Separator |
| Decimal | 31 |
| Hexadecimal | 0x1F |
| Octal | 0037 |
| Binary | 00011111 |
| HTML entity |  |
| Escape sequence | \x1F |
| Unicode | U+001F |
| Keyboard | Ctrl+_ |
| Group | Control character |
What it is for
The finest separator, dividing fields within a record — an unambiguous alternative to the comma in CSV, if anything supported it.
Where the number comes from
Codes 0 to 31 were reserved for control: instructions to a teleprinter rather than characters to print. Code 31 is Ctrl+_ because the Ctrl key was originally wired to clear the top two bits of whatever you typed, mapping the letter _ at 95 down to 31.
Frequently asked questions
What is ASCII 31?
Unit Separator (US), a control character. In hexadecimal it is 0x1F, in octal 0037, and in binary 00011111.
How do I type ASCII 31?
Press Ctrl+_ in a terminal. In a string literal you can write it as \\x1F in most languages.
Is ASCII 31 printable?
No. Codes 0 to 31 and 127 are control characters — they were instructions to a teleprinter rather than marks on paper, and most terminals show nothing for them.
Nearby codes
- ASCII 24 — CAN
- ASCII 25 — EM
- ASCII 26 — SUB
- ASCII 27 — ESC
- ASCII 28 — FS
- ASCII 29 — GS
- ASCII 30 — RS
- ASCII 32 — space
- ASCII 33 — !
- ASCII 34 — "
- ASCII 35 — #
- ASCII 36 — $
- ASCII 37 — %
- ASCII 38 — &
Full ASCII table · Text to binary converter · Number base converter