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DECFRA — fill rectangular area
CSI Pc ; Pt ; Pl ; Pb ; Pr $ xDECFRA (
CSI Pc ; Pt ; Pl ; Pb ; Pr $ x) fills a rectangular area with character Pc from rows Pt through Pb and columns Pl through Pr. Introduced on the DEC VT420 in 1990 for form-fill applications and spreadsheets that needed to paint rectangular regions of the screen — drawing dividers, padding fields, or clearing a region with a fill character — without touching cells outside the rectangle. xterm and mintty implement DECFRA; nearly every other modern terminal skips it. The character must be in the printable ASCII range or DEC supplemental graphic range.How this is testedautomated
Send
Send
\x1b[88;1;1;3;5$x (fill rows 1-3, cols 1-5 with 'X'), verify cells in the rectangle contain 'X'.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 9 tested terminals — universal adoption. Part of the Unicode baseline.
Supported by 8 of 14 backends (57%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | sequence consumed |
| Ghostty | 1.3.1 | ✓ yes | sequence consumed |
| 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 |
|---|---|---|---|
| Alacritty | 0.26.0 | ✗ no | VT420 rectangular area operations not implemented — legacy DEC features omitted by most modern terminals |
| Kitty | 0.40.0 | ✗ no | VT420 rectangular area operations not implemented — legacy DEC features omitted by most modern terminals |
| vt100.js | 0.2.1 | ✗ no | VT420 rectangular area operations not implemented — legacy DEC features omitted by most modern terminals |
| vterm | 0.2.0 | ✗ no | VT420 rectangular area operations not implemented — legacy DEC features omitted by most modern terminals |
| WezTerm | 0.1.0-fork.5 | ✗ no | VT420 rectangular area operations not implemented — legacy DEC features omitted by most modern terminals |
| xterm.js | 5.5.0 | ✗ no | VT420 rectangular area operations not implemented — legacy DEC features omitted by most modern terminals |