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Kitty keyboard protocol
ESC [ > flags uThe Kitty keyboard protocol solves fundamental ambiguities in traditional terminal input handling. Legacy terminals cannot distinguish between
Ctrl+I and Tab, Ctrl+M and Enter, or Escape and the start of an escape sequence — they all produce the same byte sequences. The protocol also enables key-release events and distinguishes between different modifier key presses (left vs. right Shift).
Applications opt in with CSI > flags u, where flags is a bitmask selecting reporting modes: disambiguate keys (1), report event types (2), report alternate keys (4), report all keys as escape sequences (8), and report associated text (16). Keys are reported as CSI unicode-key-code : shifted-key : base-layout-key ; modifiers : event-type u.
Adopted by Ghostty, WezTerm, foot, and rio. The protocol is progressive — applications can request only the features they need, and terminals report which flags they support.How this is testedautomated
Query keyboard mode flags via
Query keyboard mode flags via
CSI ? u and check for a CSI ? flags u response indicating Kitty keyboard protocol support.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 14 backends (64%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| VS Code | ✓ yes | ||
| Warp | ✓ yes | ||
| Cursor | ✗ no | ||
| Terminal.app | ✗ no |
Headless Backends
Parser correctness only — a ✓ means the parser accepts the sequence.
| Backend | Version | Support | Notes |
|---|---|---|---|
| Alacritty | 0.26.0 | ✓ yes | |
| Kitty | 0.40.0 | ✓ yes | |
| vterm | 0.2.0 | ✓ yes | |
| WezTerm | 0.1.0-fork.5 | ✓ yes | |
| vt100.js | 0.2.1 | ✗ no | Not implemented — pure TypeScript emulator |
| xterm.js | 5.5.0 | ✗ no | Not implemented in xterm.js |
Sub-features
This feature has 5 individually testable sub-features.
| Sub-feature | iTerm2 | Ghostty | VS Code | Warp | Cursor | Terminal.app |
|---|---|---|---|---|---|---|
| Kitty keyboard: DISAMBIGUATE (flag 1) | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ |
| Kitty keyboard: REPORT_ALL_KEYS (flag 8) | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ |
| Kitty keyboard: REPORT_ALTERNATE (flag 4) | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ |
| Kitty keyboard: REPORT_EVENTS (flag 2) | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ |
| Kitty keyboard: REPORT_TEXT (flag 16) | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ |