Terminal Comparison

How Otty's escape-sequence support compares to other modern terminals. Use this when porting a TUI between terminals or deciding which protocols are safe to rely on.

Methodology

Symbols:

• ✓ — fully implemented (mode is honored, response is correct)
• ◐ — partially implemented (parsed without errors, but behavior is incomplete — e.g. the iTerm2 inline-image protocol only accepts its multipart form)
• ❌ — not implemented (unknown / ignored / replied as not-supported)

The Otty column reflects what the terminal actually honors today — verified against the source, not the documentation. Where a sequence is parsed but the underlying mode is a no-op, it is marked ❌, not ✓.

Standard DEC private modes

These are the modes set with DECSET CSI ? Pn h and reset with DECRST.

Mode	Name	xterm	iTerm2	Kitty	WezTerm	Alacritty	Ghostty	Otty
?1	DECCKM — App cursor keys	✓	✓	✓	✓	✓	✓	✓
?6	DECOM — Origin mode	✓	✓	✓	✓	✓	✓	✓
?7	DECAWM — Auto-wrap	✓	✓	✓	✓	✓	✓	✓
?9	X10 mouse (legacy)	✓	✓	✓	✓	❌	✓	❌
?12	Blinking cursor	✓	✓	✓	✓	✓	✓	✓
?25	DECTCEM — Cursor visible	✓	✓	✓	✓	✓	✓	✓
?47	Alt screen (legacy)	✓	✓	✓	✓	❌	✓	✓
?1000	Mouse: button events	✓	✓	✓	✓	✓	✓	✓
?1002	Mouse: cell-motion	✓	✓	✓	✓	✓	✓	✓
?1003	Mouse: all-motion	✓	✓	✓	✓	✓	✓	✓
?1004	Focus in/out	✓	✓	✓	✓	✓	✓	✓
?1005	Mouse: UTF-8 encoding	✓	✓	✓	✓	✓	✓	✓
?1006	Mouse: SGR encoding	✓	✓	✓	✓	✓	✓	✓
?1016	Mouse: SGR-Pixel	✓	✓	✓	✓	❌	✓	❌
?1047	Alt screen + clear on exit	✓	✓	✓	✓	❌	✓	✓
?1049	Alt screen + save cursor	✓	✓	✓	✓	✓	✓	✓
?2004	Bracketed paste	✓	✓	✓	✓	✓	✓	✓
?2026	Synchronized output (BSU/ESU)	⚠️ partial	✓	✓	✓	✓	✓	✓
?2027	Grapheme-cluster mode	❌	❌	❌	❌	❌	✓	❌
?2031	Color-scheme update notify	❌	❌	✓	✓	✓	✓	✓
?2048	In-band resize notify	❌	❌	✓	✓	❌	✓	❌

Identification & queries

Sequence	What it asks	xterm	iTerm2	Kitty	WezTerm	Alacritty	Ghostty	Otty
CSI c	Primary DA	✓	✓	✓	✓	✓	✓	✓
CSI > c	Secondary DA	✓	✓	✓	✓	✓	✓	✓
CSI > q	XTVERSION	✓	✓	✓	✓	✓	✓	✓
CSI 5 n / 6 n	DSR — status / cursor pos	✓	✓	✓	✓	✓	✓	✓
CSI ? Pn $ p	DECRQM mode status	✓	✓	✓	✓	✓	✓	✓
CSI 14 t	Text-area size in px	✓	✓	✓	✓	✓	✓	✓
CSI 16 t	Cell size in px	✓	✓	✓	✓	❌	✓	✓
CSI 18 t	Text-area size in cells	✓	✓	✓	✓	✓	✓	✓
CSI 22 J	Kitty scroll-then-erase	❌	❌	✓	❌	❌	✓	✓
CSI ? u	Kitty keyboard-flags query	❌	❌	✓	✓	✓	✓	✓
DCS $ q … ST	DECRQSS — request current setting	✓	✓	✓	✓	❌	✓	◑
DCS + q … ST	XTGETTCAP — terminfo cap query	✓	❌	✓	✓	❌	✓	❌

Vendor extensions

Protocol	Sequence	Origin	xterm	iTerm2	Kitty	WezTerm	Alacritty	Ghostty	Otty
Kitty graphics	APC G …	Kitty	❌	❌	✓	✓	❌	✓	✓
iTerm2 inline image	OSC 1337 File=	iTerm2	❌	✓	❌	✓	❌	❌	◐ multipart only
Sixel	DCS q …	DEC	✓	❌	❌	✓	❌	✓	❌
Kitty keyboard	CSI > 1 u …	Kitty	❌	❌	✓	✓	✓	✓	✓
Hyperlink	OSC 8	xterm/VTE	❌	✓	✓	✓	✓	✓	✓
Clipboard	OSC 52	xterm	✓	✓	✓	✓	✓	✓	✓
Indexed palette	OSC 4 / 104	xterm	✓	✓	✓	✓	✓	✓	✓
Dynamic colors	OSC 10 / 11 / 12	xterm	✓	✓	✓	✓	✓	✓	✓
Shell integration	OSC 133 (FTCS)	FinalTerm	❌	✓	✓	✓	❌	✓	✓
VSCode shell integration	OSC 633	VSCode	❌	❌	❌	❌	❌	❌	❌
CWD report	OSC 7	VTE	❌	✓	✓	✓	❌	✓	✓
iTerm2 SetUserVar	OSC 1337 SetUserVar=	iTerm2	❌	✓	❌	✓	❌	❌	❌
ConEmu progress	OSC 9 ; 4	ConEmu	❌	❌	❌	✓	❌	✓	✓
Kitty notification	OSC 99	Kitty	❌	❌	✓	❌	❌	✓	✓
iTerm2 notification	OSC 9	iTerm2	❌	✓	❌	✓	❌	✓	✓
xterm color stack	CSI [Pm] # P/Q/R	xterm	✓	❌	❌	❌	❌	✓	✓
Terminal Resume (TRP)	OSC 88	Otty	❌	❌	❌	❌	❌	❌	◐ experimental
Program status	OSC 7501	Rex	❌	❌	❌	❌	❌	❌	✓

Behavior notes

CSI ? Pn $ p — DECRQM

Otty answers DECRQM for both ANSI modes (CSI Pn $ p) and DEC private modes (CSI ? Pn $ p), replying with DECRPM CSI ? Pn ; state $ y. The state follows the DEC convention: 1 = set, 2 = reset (supported but currently off), 4 = not recognized. Every private mode listed in the table above reports a truthful set/reset state; any mode Otty doesn't implement replies 4 rather than pretending to support it. The one nuance is ?2026: the live synchronized-output state lives inside the parser and isn't queryable, so Otty always answers 2 (reset) — which is exactly what nvim, zellij, and Ghostty probe for to decide whether to emit BSU/ESU.

CSI ? 2026 h/l — Synchronized Output

Between BSU and ESU, Otty buffers all output and paints it in a single frame, so a full-screen redraw never tears or flickers. A short safety timeout flushes the buffer if a program enables synchronized output and then dies without sending ESU, so a crash can't freeze the pane.

CSI > q — XTVERSION

Otty replies with DCS > | otty(<version>) ST, where <version> is the build version. Programs that recognize the otty( prefix can gate features on it.

Selective erase & character protection — DECSCA / DECSED / DECSEL

Otty implements the VT220 character-protection family:

• DECSCA (CSI <n> " q) marks subsequently written cells as protected (n=1) or erasable (n=0/2).
• DECSED (CSI ? <n> J) and DECSEL (CSI ? <n> K) erase only the erasable cells, leaving protected ones in place.

Protection is per-cell and independent of SGR (SGR 0 does not clear it; only DECSCA 0/2, DECSTR, or RIS do), and it is saved/restored with the cursor by DECSC / DECRC.

Support across terminals is uneven. xterm and Ghostty implement the family; Alacritty does not — it has no DECSCA and ignores the selective-erase private variants, so CSI ? 2 J finds nothing protectable and clears the screen like a plain erase. That gap is what motivated adding the family to Otty.

Notable gaps

DCS q … — Sixel

Not parsed. The underlying vte parser treats DCS hooks as no-ops and the Otty fork doesn't add a Sixel decoder. Modern equivalents (Kitty graphics) cover the same ground for new code; Sixel remains the only option for legacy tools (gnuplot, img2sixel, lsix).

DCS $ q … / DCS + q … — DECRQSS & XTGETTCAP

Partial (◑). Both are DCS-framed queries: DECRQSS asks the terminal to echo back a current setting; XTGETTCAP asks for a terminfo capability. Otty answers the cursor-style DECRQSS (DCS $ q SP q ST → DCS 1 $ r <Ps> SP q ST), so tmux and TUIs can read back the active cursor shape after a DECSCUSR change. Other DECRQSS targets (SGR, scrolling region, …) and XTGETTCAP are still not answered — vte doesn't dispatch general DCS payloads — so programs probing those fall back to their defaults.

?2048 — In-band resize notifications

Not implemented. Programs that opt in expect a CSI 48 ; … t report on every resize instead of relying on SIGWINCH. Otty ignores the DECSET and the program falls back to SIGWINCH, which works on macOS.

?1016 — SGR-Pixel mouse

Not implemented. vte doesn't recognize mode 1016, so Otty reports mouse events in cell coordinates via SGR mode (?1006) instead of pixel coordinates. Apps that request pixel precision degrade gracefully to cell precision.

OSC 633 — VSCode shell integration

Not parsed. VSCode's integrated-terminal scripts emit OSC 633 in parallel to OSC 133. Otty users running Set-PSReadLineOption-style integrations see the bracketed escapes echoed to the screen.

OSC 1337 single-segment File=

Only the multipart form is parsed. The single-segment form (OSC 1337 ; File=<base64-attrs>:<base64-data> ST) — the default emitted by imgcat and most shell scripts — is dropped. Larger images that don't fit in one OSC payload work; the common small case doesn't.

OSC 88 — Terminal Resume Protocol

Experimental and Otty-specific. The handshake is wired up — Otty parses arm / clear / query and answers query with OSC 88 ; supported ; v=1 ST — but persisting a pane's resume spec and replaying it end-to-end is still in progress. No other terminal implements OSC 88. See OSC 88 and github.com/Otty-sh/osc-88.

OSC 7501 — Program Status

The Program Status Protocol (rev 0.4), from Superlogical's Rex. Otty implements rev 0.4: all five states, blocked kinds, hierarchical ids with clear by subtree, and the ? feature query. The most urgent record drives the tab badge, the Dock icon, Inbox and notifications. Where a terminal only understands OSC 9;4, a program can send both. See OSC 7501.

See also

• VT Overview
• Sequence Reference
• External Protocols