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Primary device attributes (DA1)
ESC [ cDA1 (Primary Device Attributes) lets applications identify the terminal type and its capabilities. The query is
ESC [ c or ESC [ 0 c. The terminal responds with ESC [ ? attributes c where attributes is a semicolon-separated list of capability codes.
DA1 is one of the first sequences an application sends to discover what the terminal supports. The response identifies the terminal class (VT100, VT220, etc.) and optional capabilities. Modern terminals typically identify as VT220 or higher with various capability flags. Shell integration scripts and TUI frameworks use DA1 to enable or disable features based on terminal capabilities.How this is testedautomated
Send
Send
\x1b[c (DA1), verify response contains ? and ends with c (e.g., \x1b[?62;...c).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 12 tested terminals — universal adoption. Part of the Modern TUI baseline.
Supported by 10 of 14 backends (71%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| 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 |
|---|---|---|---|
| vt100.js | 0.2.1 | ✓ yes | No output stream — pure TypeScript emulator |
| vterm | 0.2.0 | ✓ yes | |
| Alacritty | 0.26.0 | ~ partial | Headless mode has no output stream for DA1 responses |
| Kitty | 0.40.0 | ~ partial | Headless mode has no output stream for DA1 responses |
| WezTerm | 0.1.0-fork.5 | ~ partial | Headless mode has no output stream for DA1 responses |
| xterm.js | 5.5.0 | ~ partial | Headless mode has no output stream for DA1 responses |