DECSET 12 — Cursor blink (att610)

CSI ? 12 h enables text-cursor blinking; CSI ? 12 l makes the cursor steady (no blink). This is the 'att610' cursor-blink private mode popularized by xterm. It controls blink only; the cursor SHAPE is set by DECSCUSR (CSI Ps SP q), and the two can conflict.

terminal-dec-private-mode kind control-sequence status de-facto verification verified tier B terminal-escape@1

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DEC-private-mode introducer: \x1b[? ESC [ ? (0x1B 0x5B 0x3F)

terminator (none): ST · BEL

parameters / subcommands

id	name	bytes (ST)	meaning
set	Enable (DECSET)	\x1b[?12h	CSI ? 12 h turns ON cursor blinking (att610).
reset	Disable (DECRST)	\x1b[?12l	CSI ? 12 l turns OFF blinking, giving a steady cursor.

gotchas

Mode 12 controls BLINK ONLY; the cursor SHAPE (block/underline/bar) comes from DECSCUSR (CSI Ps SP q). The two interact: DECSCUSR's odd values also imply blink, so they can fight mode 12.
This is the 'att610' (AT&T 610) blink convention; not all terminals map mode 12 the same way, and some honor only DECSCUSR.
Some terminals invert the meaning or ignore mode 12 in favor of a user preference for cursor blink.
Restore the user's preferred blink state on exit rather than forcing it.
Cursor blink is sometimes globally disabled by the OS/terminal for accessibility; your ?12h may have no visible effect.

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 2 -> Start Blinking Cursor (AT&T 610). Set = blinking cursor, reset = steady cursor.

DECSET 12 — Cursor blink (att610)

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parameters / subcommands

gotchas

provenance

see also