Appearance
Bold (SGR 1)
ESC [ 1 mSGR 1 activates bold text rendering. The sequence is
ESC [ 1 m. Bold is one of the original VT100 text attributes and is universally supported across terminals.
Historically, some terminals render SGR 1 as increased intensity (brighter color) rather than heavier font weight — and some do both. When bold is active alongside one of the standard foreground colors (SGR 30-37), certain terminals will substitute the corresponding bright color (SGR 90-97). This means bold red may appear as bright red rather than bold red, depending on the terminal and its configuration.
Bold is reset by SGR 0 (reset all) or SGR 22 (reset bold/dim). Note that SGR 22 resets both bold and faint — there is no way to reset one without the other.How this is testedautomated
Send
Send
\x1b[1mX, verify the cell at (0,0) has bold=true. Confirms the SGR 1 attribute is parsed and applied to the character cell.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 Core TUI baseline.
Supported by 14 of 14 backends (100%)
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 |