DECSET 6 — DECOM (origin mode)

CSI ? 6 h (DECOM set) makes cursor addressing relative to the scroll region (DECSTBM): row 1 becomes the top margin and the cursor cannot leave the region. CSI ? 6 l restores absolute (screen-relative) addressing. Setting or resetting DECOM also homes the cursor.

frame

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

terminator (none): ST · BEL

parameters / subcommands

id	name	bytes (ST)	meaning
set	Enable (DECSET)	\x1b[?6h	CSI ? 6 h sets DECOM: CUP/HVP coordinates become relative to the top margin of the scroll region, and the cursor is confined within the region. The cursor moves to the region's home.
reset	Disable (DECRST)	\x1b[?6l	CSI ? 6 l clears DECOM: addressing is absolute to the physical screen; the cursor moves to screen home.

gotchas

Setting OR resetting DECOM HOMES the cursor — do not assume the cursor stays put when toggling it.
Under DECOM, CUP row 1 is the scroll-region top, not the screen top; combine with DECSTBM to define the region first.
Under DECOM the cursor cannot move outside the scroll region, even with explicit CUP to an out-of-region row (it clamps).
DECOM interacts with DECSTBM: set the margins first, then enable origin mode, then address relatively.
Reset DECOM (?6l) before exit so the next program sees absolute addressing.

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 = 6 -> Origin Mode (DECOM). When set, cursor addressing is relative to the scrolling region's top margin and the cursor is confined to the region.
ext.params — https://vt100.net/docs/vt510-rm/DECOM.html DEC VT510 manual: DECOM (mode 6) selects whether line numbers are relative to the margins; changing it moves the cursor to home.

DECSET 6 — DECOM (origin mode)

frame

parameters / subcommands

gotchas

provenance

see also