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iTerm2 Cell Size Reporting (OSC 1337)
OSC 1337 ; ReportCellSize queries the terminal for the dimensions of a single character cell in pixels. The response is OSC 1337 ; ReportCellSize=height;width ST. This is essential for pixel-accurate image rendering protocols (sixel, iTerm2 inline images, kitty graphics) where applications need to know the exact pixel dimensions of cells to scale images correctly.
How this is testedautomated
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OSC 1337 ; ReportCellSize BEL and verify the terminal responds with cell dimensions.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 1 of 12 terminals (8%). Part of the Rich TUI baseline.
Supported by 1 of 14 backends (7%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✗ no | No ReportCellSize response |
| Ghostty | 1.3.1 | ✗ no | iTerm2-specific protocol not supported |
| VS Code | ✗ no | ||
| Warp | ✗ no | ||
| Cursor | ✗ no | ||
| Terminal.app | ✗ no |
Headless Backends
Parser correctness only — a ✓ means the parser accepts the sequence.
| Backend | Version | Support | Notes |
|---|---|---|---|
| vterm | 0.2.0 | ✓ yes | |
| Alacritty | 0.26.0 | ✗ no | iTerm2-specific protocol not supported |
| Kitty | 0.40.0 | ✗ no | iTerm2-specific protocol not supported by kitty |
| vt100.js | 0.2.1 | ✗ no | iTerm2-specific protocol not implemented — pure TypeScript emulator |
| WezTerm | 0.1.0-fork.5 | ✗ no | iTerm2-specific protocol not supported |
| xterm.js | 5.5.0 | ✗ no | iTerm2-specific protocol not supported |