Features›Input Protocols›X10 Mouse Tracking (9)

X10 Mouse Tracking (9)

Category: input · Baseline: modern · Tags: DEC Private Modes · Specification ↗

X10 compatibility mouse tracking (mode 9) reports only button press events, not releases or motion. This is the oldest mouse tracking mode, limited to coordinates up to 223 and press-only events.

How this is testedautomated
Enable X10 mouse mode (CSI ? 9 h), check getMode("mouseTracking") returns true.

The same probe runs against headless backends (via Termless) and real terminal apps (via a daemon launched in each terminal). This lets us distinguish parser correctness from rendering correctness.

Analysis2026-04-06

Supported by 9 of 12 terminals (75%). Not supported by: vt100.js, Alacritty, WezTerm. Part of the Modern TUI baseline. Notes: vt100.js: X10 mouse mode (?9) not implemented; Alacritty: X10 mouse mode (?9) not implemented; WezTerm: X10 mouse mode (?9) not implemented.

Supported by 10 of 14 backends (71%)

Terminal Applications

Terminal	Version	Support	Notes
iTerm2	3.6.9	✓ yes
Ghostty	1.3.1	✓ yes
VS Code		✓ yes
Warp		✓ yes
Cursor		✓ yes
Terminal.app		✓ yes

Headless Backends

Parser correctness only — a ✓ means the parser accepts the sequence.

Backend	Version	Support	Notes
vterm	0.2.0	✓ yes
xterm.js	5.5.0	✓ yes
Alacritty	0.26.0	✗ no	X10 mouse mode (?9) not implemented
Kitty	0.40.0	✗ no	X10 mouse mode (?9) not implemented in kitty
vt100.js	0.2.1	✗ no	X10 mouse mode (?9) not implemented
WezTerm	0.1.0-fork.5	✗ no	X10 mouse mode (?9) not implemented

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