Control characters and ESC sequences¶

Status: Standard (C0, C1), DEC (most ESC x commands).

Before CSI, OSC, and DCS there are single control bytes and two-byte escape commands. Every emulator implements the C0 set; the rest is uneven.

Syntax¶

ESC intermediate-bytes final-byte

ECMA-35 (ISO 2022) defines the escape sequence and ECMA-48 borrows it. Intermediate bytes are 0x20–0x2f, the final byte is 0x30–0x7e, and there is no terminator: a parser dispatches on the first byte outside the intermediate range. The byte after ESC decides which family the sequence belongs to, and the final byte's column decides who owns it.

Final byte	Class	Owner
`0x30`–`0x3f` (`0`–`?`)	`Fp`	Private: `ESC 7`, `ESC 8`, `ESC =`, `ESC >`
`0x40`–`0x5f` (`@`–`_`)	`Fe`	C1 controls: `ESC D` is IND, `ESC [` is CSI
`0x60`–`0x7e` (`–`~`)	`Fs`	Standardized single functions: `ESC c` is RIS
`0x40`–`0x7e` after an intermediate	`Ft`	Charset designations and registered functions

The second byte maps the code space:

Second byte	Family	Examples
`SP`	ACS, announce code structure	`ESC SP F`, `ESC SP G` (DEC names: S7C1T, S8C1T)
`!`, `"`	Designate a C0 or C1 set	Not seen in practice
`#`	Private and single functions	`ESC # 8` DECALN, `ESC # 3`–`# 6` line sizes
`$`	Designate a multibyte charset	`ESC $ ( Id`, `ESC $ ) Id`, …
`%`	DOCS, designate other coding system	`ESC % G` UTF-8, `ESC % @` back to ISO 2022
`&`	IRR, charset revision	Not seen in practice
`(`, `)`, `*`, `+`	Designate a 94-charset to G0–G3	`ESC ( B`, `ESC ) 0`
`-`, `.`, `/`	Designate a 96-charset to G1–G3	`ESC - A`
`0`–`?`	Private single functions	DECSC, DECRC, DECKPAM, DECKPNM
`@`–`_`	C1 controls	IND, NEL, HTS, RI, SS2, SS3, DCS, CSI, ST, OSC, PM, APC
`–`~`	Single functions	RIS

A charset identifier Id is itself intermediate-bytes final-byte: a private final byte (0–?) names a vendor set such as DEC Special Graphics, ~ names the empty set, a leading SP names a soft (DRCS) set, and anything else is a registered set from the ISO-IR register. Emulators implement a handful of these; see Encoding.

C0 controls¶

Byte	Name	Behavior
`0x00`	NUL	Ignored
`0x05`	ENQ	Answerback; xterm sends the `answerbackString` (empty by default); PuTTY sends "PuTTY"
`0x07`	BEL	Bell: audible, visual, urgency hint, or nothing; also terminates OSC
`0x08`	BS	Cursor left one column; no erase; stops at the left margin unless `?45`
`0x09`	HT	Next tab stop; stops default every 8; `HTS`/`TBC` change them
`0x0a`	LF	Cursor down; scrolls at the bottom margin; CR too under LNM
`0x0b`	VT	Same as LF
`0x0c`	FF	Same as LF
`0x0d`	CR	Column 1 (or the left margin)
`0x0e`	SO	Shift out: use the G1 charset (line drawing when `ESC ) 0`)
`0x0f`	SI	Shift in: use G0
`0x18`, `0x1a`	CAN, SUB	Abort a sequence in progress; SUB may print a reverse `?`
`0x1b`	ESC	Start of an escape sequence
`0x7f`	DEL	Ignored on output; the Backspace key sends it

Two-byte ESC commands¶

Sequence	Name	Effect
`ESC 7`	DECSC	Save cursor, attributes, charset, origin mode, pending wrap
`ESC 8`	DECRC	Restore them
`ESC =`	DECKPAM	Application keypad: keypad sends `SS3 x`
`ESC >`	DECKPNM	Normal keypad
`ESC c`	RIS	Full reset
`ESC D`	IND	Index: cursor down, scroll at the margin
`ESC E`	NEL	Next line: CR plus IND
`ESC H`	HTS	Set a tab stop at the cursor column
`ESC M`	RI	Reverse index: cursor up, scroll down at the top margin
`ESC N`, `ESC O`	SS2, SS3	Single shift; SS3 is how application-mode keys are encoded
`ESC P`	DCS	Start of a device control string
`ESC [`	CSI	Control sequence introducer
`ESC \`	ST	String terminator
`ESC ]`	OSC	Operating system command
`ESC ^`, `ESC _`	PM, APC	Privacy message, application program command (APC carries Kitty graphics)
`ESC # 8`	DECALN	Fill the screen with `E`; the classic alignment test
`ESC # 3`–`# 6`	DECDHL, DECSWL, DECDWL	Double-height and double-width lines; see Text sizing
`ESC ( C` … `ESC + C`	SCS	Designate 94-charset `C` to G0–G3: `B` ASCII, `0` DEC Special Graphics, `A` UK
`ESC - C` … `ESC / C`	SCS	Designate 96-charset `C` to G1–G3; `A` is Latin-1
`ESC % G`, `ESC % @`		Select UTF-8 / return to ISO 2022; see Encoding
`ESC SP F`, `ESC SP G`	S7C1T, S8C1T	Emit C1 controls as 7-bit or 8-bit
`ESC l`, `ESC m`		xterm: memory lock / unlock; obsolete

C1 controls¶

Each ESC x for x in 0x40–0x5f has an eight-bit alias at 0x80–0x9f. In a UTF-8 session those bytes are continuation bytes, so emulators either disable eight-bit C1 on input (kitty, foot, Ghostty, VTE) or accept them only when ESC SP G or a non-UTF-8 locale is active (xterm). Applications must send the seven-bit form.

Reports can also be emitted in eight-bit form when S8C1T is set; every serious application assumes seven-bit and sets S7C1T defensively during initialization.

Tab stops¶

HTS sets, CSI g (TBC) clears the current stop, CSI 3 g clears all, and CSI Ps I/Ps Z move by stops. DECST8C (CSI ? 5 W) resets stops to every eighth column in xterm and DEC-faithful emulators. Tab stops are one of the least-tested state items; reset(1) restores them.

Probe¶

printf '\033#8'; sleep 1; printf '\033c'       # DECALN then reset
printf '\033(0lqqqk\033(B\n'                    # line drawing: ┌───┐
printf '\005'; tools/query ''          # ENQ answerback, usually silent

Sources¶

Compatibility¶

Feature support by terminal. Imported claims have not been reverified; unknown is not unsupported.
Feature / stable ID	Alacritty	Apple Terminal	ConPTY (conhost)	Contour	DomTerm	foot	Ghostty	iTerm2	kitty	Konsole	mintty	mlterm	PuTTY	Revenant	RLogin	st	tmux	rxvt-unicode	VTE	wayst	WezTerm	Windows Terminal	xterm	xterm.js
ESC % G / ESC % @ `esc-percent-encoding`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	SupportedImported · unverified	Unknown
CHT cursor forward tabulation `csi-cht`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
CBT cursor backward tabulation `csi-cbt`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
TBC tab clear `csi-tbc`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
NUL `c0-0x00-nul`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
BEL `c0-0x07-bel`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
BS `c0-0x08-bs`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
HT `c0-0x09-ht`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
LF `c0-0x0a-lf`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
VT `c0-0x0b-vt`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
FF `c0-0x0c-ff`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
CR `c0-0x0d-cr`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
SO `c0-0x0e-so`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
SI `c0-0x0f-si`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
CAN, SUB `c0-0x18-0x1a-can-sub`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
ESC `c0-0x1b-esc`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
DEL `c0-0x7f-del`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
DECSC `esc-decsc`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
DECRC `esc-decrc`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
DECKPAM `esc-deckpam`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
DECKPNM `esc-deckpnm`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
RIS `esc-ris`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
IND `esc-ind`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
NEL `esc-nel`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
HTS `esc-hts`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
RI `esc-ri`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
SS2, SS3 `esc-ss2-ss3`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
DCS `esc-dcs`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
CSI `esc-csi`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
ST `esc-st`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
OSC `esc-osc`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
PM, APC `esc-pm-apc`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
DECALN `esc-decaln`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
DECDHL, DECSWL, DECDWL `esc-decdhl-decswl-decdwl`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
SCS `esc-scs`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
S7C1T, S8C1T `esc-s7c1t-s8c1t`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
ENQ `c0-enq-answerback`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Supported	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown
xterm: memory lock / unlock `esc-memory-lock`	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown	Unknown