OSC 11 — Set / query default background color

OSC 11 ; spec ST sets the terminal's default background color; OSC 11 ; ? ST queries it, replied as OSC 11 ; rgb:RRRR/GGGG/BBBB ST. Programs query OSC 11 to detect a light-vs-dark background and adapt their colors. Mirrors OSC 10 for the foreground.

terminal-osc kind control-sequence status de-facto verification verified tier B terminal-escape@1

aka: set background color · query background · OSC 11 · ESC ] 11 · default bg · detect dark mode

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OSC introducer: \x1b] ESC ] (0x1B 0x5D)

terminator (ST|BEL): ST \x1b\ · BEL \x07

parameters / subcommands

id	name	bytes (ST)	meaning
set	Set default background	\x1b]11;#000000\x1b\	OSC 11 ; spec ST sets the default background color (X11 name or rgb:/# form).
query	Query default background	\x1b]11;?\x1b\	OSC 11 ; ? ST asks for the current background; reply OSC 11 ; rgb:RRRR/GGGG/BBBB ST. The de-facto way to detect light vs dark themes.

gotchas

Querying OSC 11 is the de-facto light/dark detection: parse the reply's RGB and compute luminance. Always read with a timeout — some terminals/multiplexers don't answer.
Reply is 16-bit-per-channel rgb:RRRR/GGGG/BBBB.
OSC 10/11/12 consume successive parameters; sending 'OSC 11 ; bg ST' sets only the background.
tmux/screen may swallow or proxy OSC 11 queries; passthrough config can be required for the reply to reach your program.
Reset with OSC 111 (reset background) and restore on exit.

provenance

source: https://invisible-island.net/xterm/ctlseqs/ctlseqs.html
version: xterm ctlseqs, patch #410, 2026/04/19
retrieved: 2026-05-29 · updated: 2026-05-29T00:00:00Z

per-fact attribution:

#summary — https://invisible-island.net/xterm/ctlseqs/ctlseqs.html xterm ctlseqs: Ps = 1 1 -> Change VT100 text background color to Pt; '?' queries and the terminal reports the color back.

agent: curl -H 'accept: application/json' wire.phall.io/terminal-osc/11 or /terminal-osc/11.json

OSC 11 — Set / query default background color

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parameters / subcommands

gotchas

provenance

see also