Alacritty vs xterm.js

Side-by-side terminal feature comparison

Summary

Alacritty

71%

107/151 passed

26 partial

vs

xterm.js

77%

113/147 passed

13 partial

29 features differ between these terminals

Feature Comparison

Character Sets

Feature	Alacritty	xterm.js
DEC line drawing character set	✓	✓
DEC Special Graphics	✓	✓
G0/G1 character set switching	✓	✓
UTF-8 mode	✓	✓

Cursor

Feature	Alacritty	xterm.js
CUD stops at bottom	✓	✓
CUP at screen boundaries	✓	✓
CUP with DECOM	✓	✓
CUU stops at top	✓	✓
Hide cursor (DECTCEM)	✓	~
Cursor horizontal absolute (CHA)	✓	✓
Cursor position (CUP)	✓	✓
Cursor back (CUB)	✓	✓
Cursor down (CUD)	✓	✓
Cursor forward (CUF)	✓	✓
Cursor home	✓	✓
Cursor up (CUU)	✓	✓
Cursor next line (CNL)	✓	✓
Cursor position report (DSR 6)	~	~
Reverse Wrap (Mode 45)	✗	✓
Save/restore cursor (DECSC)	✓	✓
Cursor shape (DECSCUSR)	✓	~

Device Status

Feature	Alacritty	xterm.js
Mode Report (DECRPM)	~	✓
Request Setting (DECRQSS)	~	✓
Primary device attributes (DA1)	~	~
Secondary Device Attributes (DA2)	~	✓
Device status report (DSR 5)	~	~
Feature Reporting (TERM_FEATURES)	?	?
Tertiary Device Attributes (DA3)	~	✗
Query Terminfo (XTGETTCAP)	~	✗
Terminal Version (XTVERSION)	~	✓

Editing

Feature	Alacritty	xterm.js
Delete characters (DCH)	✓	✓
Delete lines (DL)	✓	✓
Insert characters (ICH)	✓	✓
Insert lines (IL)	✓	✓
Repeat character (REP)	✓	✓

Erase

Feature	Alacritty	xterm.js
Erase character (ECH)	✓	✓
ED at scroll region boundary	✓	✓
EL erases with bg color	✓	✓
Erase line (EL 2)	✓	✓
Erase to BOL (EL 1)	✓	✓
Erase to EOL (EL 0)	✓	✓
Erase above (ED 1)	✓	✓
Erase screen (ED 2)	✗	✓
Erase below (ED 0)	✓	✓
Erase scrollback (ED 3)	✓	✓
Selective Erase (DECSED)	✗	✓

Extensions

Feature	Alacritty	xterm.js
iTerm2 Inline Images (OSC 1337)	✗	✗
Kitty graphics protocol	✗	✗
Kitty keyboard protocol	✓	✗
Desktop Notifications (OSC 9/777)	~	✗
VS Code Shell Integration (OSC 633)	✗	✗
Icon and title (OSC 0)	✓	✓
Foreground color query (OSC 10)	~	~
Background color query (OSC 11)	~	~
iTerm2 Capability Reporting (OSC 1337)	✗	✗
iTerm2 Cell Size Reporting (OSC 1337)	✗	✗
Window title (OSC 2)	✓	✓
Clipboard access (OSC 52)	~	~
OSC 5522 advanced clipboard	✗	?
OSC 66 text sizing	✗	?
Current directory (OSC 7)	~	✗
Hyperlinks (OSC 8)	✓	✓
Text reflow on resize	✓	✓
Semantic prompts (OSC 133)	✗	✗
Sixel graphics	✗	✗
Sixel support in DA1	✗	✗
24-bit truecolor	✓	✓

Input Protocols

Feature	Alacritty	xterm.js
Button-Event Mouse (1002)	✓	✓
CSI u Key Encoding	✓	✗
modifyOtherKeys	~	✗
modifyOtherKeys mode 3	~	?
Pixel Mouse Reporting (1016)	~	✗
urxvt Mouse Reporting (1015)	✗	✗
X10 Mouse Tracking (9)	✗	✓

Modes

Feature	Alacritty	xterm.js
Enter alt screen (DECSET 1049)	✓	✓
Exit alt screen (DECRST 1049)	✓	✓
App cursor keys (DECCKM)	✓	✓
Application keypad (DECKPAM)	✓	✓
Auto-wrap (DECAWM)	✓	✓
Bracketed paste (DECSET 2004)	✓	✓
Mode 2031 color scheme reporting	✗	?
Focus tracking (DECSET 1004)	✓	✓
Insert/replace mode (IRM)	✓	✓
Left/Right Margins (DECLRMM, Mode 69)	~	✗
All motion mouse (DECSET 1003)	✓	✓
SGR mouse mode (DECSET 1006)	~	~
Mouse tracking (DECSET 1000)	✓	✓
Origin mode (DECOM)	✓	✓
Reverse video (DECSCNM)	~	~
Synchronized output (DECSET 2026)	✓	✓

Reset

Feature	Alacritty	xterm.js
Backend reset() method	✓	✓
Full reset (RIS)	✓	✓
SGR reset clears attributes	✓	✓
Soft reset (DECSTR)	~	✓

Scrollback

Feature	Alacritty	xterm.js
Scrollback accumulates	✓	✓
Alt screen separate scrollback	✓	✓
DECSTBM constrains scrolling	✓	✓
DECSTBM reset to full screen	✓	✓
Reverse index (RI)	✓	✓
Scroll down (SD)	✓	✓
Scroll up (SU)	✓	~
Scroll region (DECSTBM)	✓	✓
Total line count	✓	✓

SGR (Text Styling)

Feature	Alacritty	xterm.js
256-color bg (SGR 48;5)	✓	✓
Bright bg colors (SGR 100-107)	✓	✓
Default bg color (SGR 49)	✓	✓
Standard bg colors (SGR 40-47)	✓	✓
24-bit bg (SGR 48;2)	✓	✓
Blink (SGR 5)	~	~
Bold (SGR 1)	✓	✓
Faint/dim (SGR 2)	✓	✓
256-color fg (SGR 38;5)	✓	✓
Bright fg colors (SGR 90-97)	✓	✓
Default fg color (SGR 39)	✓	✓
Standard fg colors (SGR 30-37)	~	✓
24-bit fg (SGR 38;2)	✓	✓
Hidden/invisible (SGR 8)	~	~
Inverse video (SGR 7)	✓	✓
Italic (SGR 3)	✓	✓
Overline (SGR 53)	✓	✓
Reset all (SGR 0)	✓	✓
Reset bold/dim (SGR 22)	✓	✓
Reset inverse (SGR 27)	✓	✓
Reset italic (SGR 23)	✓	✓
Reset underline (SGR 24)	✓	✓
Strikethrough (SGR 9)	✓	✓
Underline color (SGR 58)	~	✓
Curly underline (SGR 4:3)	✓	✓
Dashed underline (SGR 4:5)	✓	✓
Dotted underline (SGR 4:4)	✓	✓
Double underline (SGR 21)	~	✓
Underline (SGR 4)	✓	✓

Text

Feature	Alacritty	xterm.js
Backspace (BS)	✓	✓
Basic text rendering	✓	✓
Combining characters (0 cols)	✓	✓
Carriage return	✓	✓
Index (IND)	✓	✓
Line feed	✓	✓
Next line (NEL)	✓	✓
Overwrite at cursor	✓	✓
Reverse Index at Scroll Top	✓	✓
Tab stops	✓	✓
CJK wide chars (2 cols)	✓	✓
Emoji wide chars (2 cols)	✓	✗
Regional indicator flags (2 cols)	✗	✗
Variation selector 16 (emoji presentation)	✗	✗
Emoji ZWJ sequences (2 cols)	✓	✓
Text wraps at width	✓	✓

Unicode

Feature	Alacritty	xterm.js
East Asian Ambiguous Width	✓	✓
Grapheme Cluster Cursor Movement	✓	✓
Tab Stops (HT)	✓	✓
Wide Char at Line Wrap	✓	✓

Only in Alacritty

11 features supported by Alacritty but not xterm.js:

• Tertiary Device Attributes (DA3)Device Status
• Query Terminfo (XTGETTCAP)Device Status
• Kitty keyboard protocolExtensions
• Desktop Notifications (OSC 9/777)Extensions
• Current directory (OSC 7)Extensions
• CSI u Key EncodingInput Protocols
• modifyOtherKeysInput Protocols
• modifyOtherKeys mode 3Input Protocols
• Pixel Mouse Reporting (1016)Input Protocols
• Left/Right Margins (DECLRMM, Mode 69)Modes
• Emoji wide chars (2 cols)Text

Only in xterm.js

4 features supported by xterm.js but not Alacritty:

• Reverse Wrap (Mode 45)Cursor
• Erase screen (ED 2)Erase
• Selective Erase (DECSED)Erase
• X10 Mouse Tracking (9)Input Protocols

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