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X10 Mouse Tracking (9)
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.
X10 mode is the ancestor of terminal mouse reporting. It came from xterm and reports only button presses using compact byte-encoded coordinates, which creates the classic 223-column limit. Modern applications should prefer SGR mouse, but X10 remains useful for understanding the compatibility stack that later mouse modes extended.
How this is testedautomated
Enable X10 mouse mode (
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.
Analysis2026-05-17
Supported by 11 of 14 backends (79%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| VS Code | ✓ yes | ||
| Warp | ✓ yes | ||
| Kitty | 0.46.2 | ✓ yes | X10 mouse mode (?9) not implemented in kitty |
| Cursor | ✓ yes | ||
| Terminal.app | ✓ yes |
Headless Backends
Parser correctness only — a ✓ means the parser accepts the sequence.
| Backend | Version | Support | Notes |
|---|---|---|---|
| vterm.js | 0.2.0 | ✓ yes | |
| xterm.js | 5.5.0 | ✓ yes | |
| Alacritty | 0.26.0 | ✗ no | X10 mouse mode (?9) not implemented |
| 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 |