# Set X Property (OSC 3)

> Set or delete a property on the terminal's top-level X window.

- **Sequence:** `OSC 3 ; prop = value ST`
- **ECMA-48:** [§8.3.89 OSC – Operating System Command, p. 51](https://archive.org/details/ecma-48-5th-edition-june-1991/page/n64/mode/1up)
- **xterm:** [Operating System Commands](https://invisible-island.net/xterm/ctlseqs/ctlseqs.html)

`OSC 3 ; prop=value ST` sets the property `prop` of xterm's top-level X
window to `value`, and `OSC 3 ; prop ST` deletes it, so that a program can
leave information on the window for the window manager or for scripts that
look at X properties
([`ChangeXprop`](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/misc.c#L6380-L6401)).
The number came from dtterm, which used it to set the working directory for
the next session; xterm does that with its `spawn-new-terminal` action
instead.

A default xterm does not do it. Setting a property is one of the *window
operations* off unless `allowWindowOps` is set: `SetXprop` is in the
default `disallowedWindowOps`
([`main.h`](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/main.h#L150-L175),
[`do_osc`](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/misc.c#L4183-L4187)).
X properties do not exist outside X, and libghostty-vt has no `OSC 3`: it
ignores it. Both leave the screen and the title as they were, and the cases
pass.

## Support

| Terminal | Version | Support | Notes |
| --- | --- | --- | --- |
| VT220 | [manual](https://vt100.net/docs/vt220-rm/), 2nd ed., 1984 | No | OSC is not among the controls it recognizes ([§4.2](https://vt100.net/docs/vt220-rm/chapter4.html#S4.2)) |
| VT510 | [manual](https://vt100.net/docs/vt510-rm/), 1st ed., 1993 | No | ignores an OSC string ([chapter 4](https://vt100.net/docs/vt510-rm/chapter4.html)) |
| xterm | patch 412, [xterm-411a](https://github.com/ThomasDickey/xterm-snapshots/tree/xterm-411a) | Partly | off unless `allowWindowOps` is set; `SetXprop` is disallowed by default |
| libghostty-vt | [0f171f6](https://github.com/ghostty-org/ghostty/tree/0f171f650a1cbbd6df4a2573b6b0c7de57cc6d90) | No | ignored |
| Konsole | 26.11.70, [a24c3d71](https://invent.kde.org/utilities/konsole/-/tree/a24c3d71be3684f24d030aa2dbe9bd723d985233) | No | not in its source |
| ConEmu | build 230724, its [documentation](https://conemu.github.io/en/AnsiEscapeCodes.html) | No | not in its [ANSI escape codes](https://conemu.github.io/en/AnsiEscapeCodes.html) |

## Validation

### OSC3-1: Nothing changes

Input, one step per line:

```text
\e]2;Window\a
A
\e]3;WM_ROLE=terminal\a
\e]3;WM_ROLE\a   # delete it
B
```

Expected screen:

```text
|AB____|
cursor 1,3
title "Window"
reply none
```

---

This is the Markdown version of <https://control-codes.page/osc/x-property/>. On that page every validation case runs live in libghostty-vt, the terminal emulation core of Ghostty, compiled to WebAssembly.

The validation cases are written in the notation described in <https://control-codes.page/notation/index.html.md>.