SGR — Select Graphic Rendition

Sequence	CSI <p1> ; <p2> ; … m
Bytes	0x1B 0x5B <params> 0x6D
Category	CSI
Mnemonic	SGR
Otty support	✓ Implemented (full standard + extended underlines + RGB)

Description

Sets graphic rendition for subsequent characters — foreground / background color, weight, italic, underline, strike-through, etc. Parameters are 1+ numeric codes separated by ; (or : for sub-parameters); multiple codes apply in order.

CSI m (no parameters) and CSI 0 m both reset all attributes.

Common parameters

Param	Effect
0	Reset
1	Bold
2	Dim
3	Italic
4	Underline
5	Blink
7	Reverse video
8	Conceal
9	Strike-through
21	Double underline
22	Reset bold/dim
23	Reset italic
24	Reset underline
30–37	Foreground ANSI 0-7
38;5;<n>	Foreground 256-color
38;2;<r>;<g>;<b>	Foreground 24-bit
39	Default foreground
40–47	Background ANSI 0-7
48;5;<n>	Background 256-color
48;2;<r>;<g>;<b>	Background 24-bit
49	Default background
90–97	Foreground bright 0-7
100–107	Background bright 0-7

Extended underlines

Using : sub-parameters (the kitty / iTerm2 / WezTerm convention). All five styles render in Otty:

Sub-param	Style	Otty rendering
4:0	None	clears underline
4:1	Single	2 px underline (also via plain \e[4m)
4:2	Double	two stacked 2 px lines (use 4:2, not \e[21m — under ECMA-48, 21 resets bold)
4:3	Curly (undercurl)	square-wave wavy line, fg or SGR 58 colored
4:4	Dotted	repeating dot pattern
4:5	Dashed	repeating short-dash pattern
58:5:<n> or 58:2::<r>:<g>:<b>	Underline color (independent of text color)	applied to single / double / curly / dotted / dashed
59	Reset underline color	back to text color

Note: kitty's writers usually emit the colon form 58:2::R:G:B (the empty colorspace slot before the RGB triple); the semicolon form 58;2;R;G;B is also accepted.

Example

# Bold red text
printf '\e[1;31mERROR\e[0m\n'

# 24-bit color
printf '\e[38;2;127;90;240mpurple\e[0m\n'

# Curly red underline beneath default-colored text — the SGR 58 form
# nvim's LSP uses for error squiggles
printf '\e[4:3;58:2::255:100:100mtypo\e[0m\n'

# Dashed green underline (warnings)
printf '\e[4:5;58:2::120:255:120mTODO\e[0m\n'

# Try every style at once:
otty features try styles

Try it

• otty features try styles — bold / italic / underline / strike / reverse / blink sampler.
• otty features try true-color — 24-bit gradient strip across bg and fg.
• otty features try text-style — ASCII × CJK trait stress (catches font-cascade slips).
• otty features try font-blending — same line on dark / medium / light bg for comparing font-blending modes.
• otty features try change-color — interactive OSC 10/11/12/17/19 + XTPUSHCOLORS picker.

Notes

• Parameter 1 (bold) renders in the bright palette when bold-is-bright = on (config). Off by default.
• Otty caps SGR parsing at 256 parameters per sequence; very long chains beyond that are truncated.
• Some terminals interpret 1 as a "bright" hint instead of bold weight; Otty applies real weight from the font.

Related

• Unicode and Text Styles — how SGR maps to glyph drawing.
• Themes — palette that ANSI codes (30-37 / 40-47 etc.) reference.