Features›SGR (Text Styling)›Dotted underline (SGR 4:4)

Dotted underline (SGR 4:4)

Category: sgr · Baseline: modern · Tags: Kitty Extensions · Specification ↗

ESC [ 4:4 m

SGR 4:4 draws a dotted underline beneath text: ESC [ 4:4 m. Part of the Kitty extended underline styles. Can be combined with SGR 58 for colored underlines. Reset with SGR 24.

How this is testedautomated
Send \x1b[4:4mX, verify underline === "dotted".

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 11 of 12 terminals (92%). Not supported by: vt100.js. Part of the Modern TUI baseline. Notes: vt100.js: Not in VT100/VT220 — only single underline supported.

Supported by 13 of 14 backends (93%)

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
Alacritty	0.26.0	✓ yes
Kitty	0.40.0	✓ yes
vterm	0.2.0	✓ yes
WezTerm	0.1.0-fork.5	✓ yes
xterm.js	5.5.0	✓ yes
vt100.js	0.2.1	✗ no	Not in VT100/VT220 — only single underline supported

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