Skip to content

CSI queries and reports

Status: Standard (DSR, DA), DEC (DECRQM, DA2, DA3), xterm (XTVERSION and window reports).

Some controls produce bytes in the reverse direction. The application writes a query to terminal output; the terminal writes its report to PTY input, where it is interleaved with keyboard and mouse events.

Window Ops: the CSI … t geometry reports below belong to xterm's Window Ops policy and are allowed by default. This label does not apply to every query on this page.

Common exchanges

Request Report Purpose
CSI 5 n CSI 0 n Device status: "OK"
CSI 6 n CSI row ; col R Cursor position (CPR); relative to origin under DECOM
CSI ? 6 n CSI ? row ; col R Extended CPR (DECXCPR); unambiguous against CSI 1;1 R F3 reports
CSI c / CSI 0 c CSI ? Pm c Primary device attributes (DA1): conformance level and feature list
CSI > c CSI > Pp ; Pv ; Pc c Secondary DA: terminal type, version, ROM cartridge
CSI = c DCS ! \| hex ST Tertiary DA: unit id; mostly zeros
CSI > 0 q DCS > \| name ( version ) ST XTVERSION; see XTVERSION
CSI ? Ps $ p CSI ? Ps ; Pm $ y DECRQM; see Modes
CSI ? u CSI ? flags u Kitty keyboard flags; see Input
CSI Ps t (14, 16, 18) CSI Ps ; h ; w t Window sizes; see Window operations
CSI ? Pi ; Pa ; Pv S CSI ? Pi ; Ps ; Pv S XTSMGRAPHICS: Sixel registers and geometry
DCS $ q Pt ST DCS 1 $ r … ST DECRQSS; see DCS
DCS + q hex ST DCS 1 + r … ST XTGETTCAP; see DCS
OSC 10 ; ? ST OSC 10 ; rgb:… ST Color queries; see OSC colors

Device attributes

DA1 is the oldest and most reliable "is anyone there" probe. Every emulator answers, and the answer identifies a DEC conformance level and features:

Reply Claimed identity Feature codes seen
CSI ? 1 ; 2 c VT100 with AVO
CSI ? 6 c VT102 Common in minimal emulators
CSI ? 62 ; … c VT220 1 132 columns, 2 printer, 4 Sixel, 6 selective erase, 9 NRCS, 15 technical charset, 16 locator, 17 terminal state, 18 windowing, 21 horizontal scrolling, 22 color, 28 rectangular editing, 29 ANSI text locator
CSI ? 63 ; … c, 64, 65 VT320, VT420, VT520 Same list

Feature 4 is the only sanctioned Sixel detection. xterm's default reply depends on decTerminalID; kitty answers CSI ? 62 ; c; Windows Terminal answers as a VT220 with 1;4;6;7;14;21;22;23;24;28;32;42 (feature 4 present since 1.22); Alacritty CSI ? 6 c.

DA2 replies CSI > Pp ; Pv ; Pc c where Pp is a terminal type (0 VT100, 1 VT220, 41 VT420, 61 VT510, 64 VT520) and Pv a version. xterm reports its patch level as Pv; many emulators copy CSI > 1 ; 10 ; 0 c or CSI > 0 ; 95 ; 0 c verbatim and the number means nothing. Use XTVERSION for identification, DA2 only as a fallback.

Application requirements

Reports are asynchronous input. A robust application must:

  • put the terminal in raw or cbreak mode before writing the query;
  • distinguish reports from user input and from enabled mouse and focus protocols, which share final bytes (R from CPR and from F3 with modifiers under some encodings);
  • accept reports split across reads or adjacent to other input;
  • impose a timeout without assuming unsupported terminals reply;
  • restore input modes even if the query fails;
  • never pass reply bytes to a shell, a format string, or a title.

A reliable pattern sends the uncertain query followed by DA1 in one write. DA1 always answers, so if DA1's reply arrives without the other, the other is unsupported and no timeout is needed:

printf '\033[?u\033[c'      # kitty keyboard flags, then DA1

Sending a query and immediately performing a blocking read is unsafe when another input consumer can run concurrently; multiplexers, editors with job control, and shells with asynchronous plugins all do this.

Emulator requirements

An emulator should generate each report as one logical write and enqueue it through the same lossless PTY-input path used for encoded keys, mouse reports, and focus reports. A short write must not truncate the response.

Answers should reflect the terminal state associated with the query, not stale renderer state; CPR after a sequence of cursor moves must report the final position even if nothing has been drawn.

Unsupported or disallowed queries should follow the protocol: DECRQM answers 0, DECRQSS answers invalid, XTGETTCAP answers DCS 0 + r ST, XTVERSION and OSC color queries answer nothing. Inventing plausible responses is worse than silence because it defeats the DA1 fallback.

Multiplexers

tmux answers DA, DSR, and DECRQM itself from its own model of the pane and does not relay most queries to the outer terminal; XTVERSION reports tmux 3.x. Applications under tmux therefore see tmux's capabilities, which is the intended behavior and the reason tmux has terminal-features.

Probe

tools/query da1 da2 version
tools/query cursor
tools/query '\033[?6n'          # DECXCPR
tools/query -r da1 | od -c      # raw bytes

Sources

Compatibility

Feature support by terminal. Imported claims have not been reverified; unknown is not unsupported.
Feature / stable ID Alacritty Apple Terminal ConPTY (conhost) Contour DomTerm foot Ghostty iTerm2 kitty Konsole mintty mlterm PuTTY Revenant RLogin st tmux rxvt-unicode VTE wayst WezTerm Windows Terminal xterm xterm.js
DA1 primary device attributes
csi-da1		 Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Supported Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown
DA2 secondary device attributes
csi-da2		 Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Supported Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown
DA3 tertiary device attributes
csi-da3		 Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Supported Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown
DSR device status report; 6 n requests CPR
csi-dsr		 Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown
DEC device status reports
csi-dec-dsr		 Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown