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 tested: 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.Analysis2026-03-26
Supported by all 8 tested terminals — universal adoption. Part of the Core TUI baseline.
Supported by 13 of 13 backends (100%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| VS Code | 1.112.0 | ✓ yes | |
| Warp | 0.2026.03.18.08.24.03 | ✓ yes | |
| Cursor | 2.6.21 | ✓ yes | |
| tmux | 3.6a | ✓ yes | |
| Kitty | 0.46.2 | ✓ yes | |
| Terminal.app | 2.15 | ✓ yes | |
| GNU Screen | 5.0.1 | ✓ yes |