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Font size query/set (OSC 7770)
ESC ] 7770 ; size BELOSC 7770 queries or sets the terminal's current font size. To set:
ESC ] 7770 ; size BEL where size is a point value. To query: ESC ] 7770 ; ? BEL, and the terminal responds with the current font size. This is a mintty extension, originally added so shell scripts and TUIs running in mintty (Cygwin, MSYS, Git Bash) could programmatically zoom in or out — the same operation users perform with Ctrl+Plus / Ctrl+Minus. No other major terminal implements OSC 7770; font sizing is normally a user-only setting.How this is testedpartial
Send
Send
OSC 7770 ; ? BEL and verify the terminal responds with a font size or silently consumes the query.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 all 4 tested terminals — universal adoption. Part of the Rich TUI baseline.
Supported by 6 of 14 backends (43%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| Terminal.app | 2.15 | ✓ yes | |
| Kitty | 0.46.2 | ✓ yes | |
| VS Code | 1.113.0 | ? unknown | |
| Warp | 0.2026.03.18.08.24.03 | ? unknown | |
| Cursor | 2.6.21 | ? unknown |