# Scroll the View (OSC 720 and 721)

> Move rxvt-unicode's view up or down its scrollback, or clear the scrollback.

- **Sequence:** `OSC 720 ; Pn 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)
- **Specification:** [urxvt(7), XTerm Operating System Commands](http://pod.tst.eu/http://cvs.schmorp.de/rxvt-unicode/doc/rxvt.7.pod#XTerm_Operating_System_Commands)

`OSC 720 ; Pn ST` moves rxvt-unicode's view up its scrollback by `Pn`
lines, and `OSC 721 ; Pn ST` down it, as far as there is scrollback to
move through. Neither changes the screen's contents or the cursor, only
which lines are in view; [SU and SD](https://control-codes.page/csi/su/index.html.md) move the text instead. A
`Pn` of 0 clears the scrollback, and since rxvt-unicode reads `Pn` as a
number with nothing to say it was not one, so does an empty or non-numeric
`Pn` ([`urxvt(7)`](http://pod.tst.eu/http://cvs.schmorp.de/rxvt-unicode/doc/rxvt.7.pod#XTerm_Operating_System_Commands)).

A default xterm has no `OSC 720` and ignores it
([the OSC numbers it knows](https://github.com/ThomasDickey/xterm-snapshots/blob/xterm-411a/misc.c#L3476-L3504)).
The cases follow xterm.

libghostty-vt does not recognize `OSC 720` either: its OSC parser in
`osc.zig` has no state for the number, so the string is dropped, and the
cases pass. The same holds for 721.

## 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) | No | ignored |
| libghostty-vt | [83edd49](https://github.com/ghostty-org/ghostty/tree/83edd491e3024ae5e50393d62877b8897da1cccd) | No | ignored |
| Konsole | 26.11.70, [a24c3d71](https://invent.kde.org/utilities/konsole/-/tree/a24c3d71be3684f24d030aa2dbe9bd723d985233) | No | not among the OSC numbers it handles ([`Vt102Emulation.h`](https://invent.kde.org/utilities/konsole/-/blob/a24c3d71be3684f24d030aa2dbe9bd723d985233/src/Vt102Emulation.h#L189-L205)) |
| 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) |
| rxvt-unicode | 9.31, [`urxvtperl(3)`](https://manpages.debian.org/testing/rxvt-unicode/urxvtperl.3.en.html) | Yes | 720 and 721; 0 clears the scrollback ([`urxvt(7)`](http://pod.tst.eu/http://cvs.schmorp.de/rxvt-unicode/doc/rxvt.7.pod#XTerm_Operating_System_Commands)) |

## Validation

### OSC720-1: The screen is left as it was

Input, one step per line:

```text
AB\r\n
CD
\e]720;1\a
\e]721;1\a
```

Expected screen:

```text
|AB___|
|CD___|
cursor 2,3
reply none
```

### OSC720-2: Nor does 0 erase anything

Input, one step per line:

```text
AB
\e]720;0\a
```

Expected screen:

```text
|AB___|
cursor 1,3
```

---

This is the Markdown version of <https://control-codes.page/osc/scroll-view/>. 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>.