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DECRQCRA — checksum rectangular area
CSI Pid ; Ppid ; Pt ; Pl ; Pb ; Pr * yDECRQCRA (
CSI Pid ; Ppid ; Pt ; Pl ; Pb ; Pr * y) computes a 16-bit checksum of the cells in a rectangular region and reports it back to the host as a DCS response (DCS Pid ! ~ checksum ST). Pid is a request identifier echoed in the response; Ppid is the page number. The checksum hashes both characters and SGR attributes, which is why it's used by DEC's terminal conformance test suites — a test script can paint a known pattern, ask the terminal for the checksum, and compare against an expected value to confirm the terminal rendered the pattern correctly. xterm still implements this. Almost no application has ever used it outside of test suites.How this is testedautomated
Send
Send
\x1b[1;1;1;1;1;1*y (checksum cell 1,1), verify the sequence is consumed without literal output.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 4 of 14 backends (29%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | sequence consumed |
| Ghostty | 1.3.1 | ✓ yes | sequence consumed |
| 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 |
|---|---|---|---|
| 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 |