# Buffer Capture (XTCAPTURE) > A proposal for a program to ask its terminal for the text of its last lines, scrollback included, for a fuzzy finder or the like to search. - **Sequence:** `CSI > Pl ; Pr , t` - **Specification:** [Buffer Capture, Contour VT extensions](https://github.com/contour-terminal/contour/blob/3cdeed6c07ea892c3419a58d1d0a4c8b2d932519/docs/vt-extensions/buffer-capture.md) *Buffer Capture* lets a program ask its terminal for the text of the last lines on it, reaching back into the scrollback, so that a shell can hand what was on the screen to a tool such as `fzf` to search and pick from. It is Contour's, which names it XTCAPTURE. Its definition is [Buffer Capture](https://github.com/contour-terminal/contour/blob/3cdeed6c07ea892c3419a58d1d0a4c8b2d932519/docs/vt-extensions/buffer-capture.md), kept with Contour's other VT extensions, read at commit `3cdeed6`, and the details below that the specification leaves out are from Contour's source at release 0.8.0. No other terminal is known to implement it, and libghostty-vt does not. ## The request ``` CSI > Pl ; Pr , t ``` `Pl` is `1` to count logical lines, where a line that wrapped across several rows of the screen is one line, and `0` to count rows; Contour takes `0` when it is left out and ignores the request for any other value. `Pr` is how many to capture, counting up from the bottom of the page; left out, it is the height of the page ([`CAPTURE`](https://github.com/contour-terminal/contour/blob/v0.8.0.9335/src/vtbackend/screen/Screen.cpp#L4481-L4500)). A count larger than the page reaches into the scrollback, as far as the scrollback goes. The `,` intermediate is new. Contour first used `CSI > Pl ; Pr t`, which is xterm's XTSMTITLE, the sequence that sets how xterm encodes titles, and the specification now gives that form up to xterm. ## The answer ``` PM 314 ; data ST ``` The text comes back in [privacy messages](https://control-codes.page/esc/sos/index.html.md), as many as it takes, followed by one with no data, `PM 314 ; ST`, which ends the answer. `data` is the captured text in UTF-8, each line followed by LF. Contour sends at most 4096 bytes of text in each message, and cuts the text wherever that limit falls, so one character's bytes can be split between two messages; a reader joins the messages before decoding them. Each line loses its trailing blanks, and a line left empty is left out altogether rather than sent as a bare LF. Counting logical lines, a row that continues a wrapped line is joined to the one before without an LF. Contour always reads the main screen, even while the alternate screen is showing ([`Screen::captureBuffer`](https://github.com/contour-terminal/contour/blob/v0.8.0.9335/src/vtbackend/screen/Screen.cpp#L2576-L2647)). ## Permission Handing over the screen and its scrollback is something the user may not want, so a capture waits on Contour's `capture_buffer` permission: `allow`, `deny`, or `ask`, which is the default and asks the user. A refused request is still answered, with the closing `PM 314 ; ST` and nothing before it, because the protocol has no way to say that no answer is coming and a program reading up to the end would otherwise wait forever. A refusal therefore cannot be told apart from capturing a blank screen, and the specification says that is deliberate ([`TerminalSession.cpp`](https://github.com/contour-terminal/contour/blob/v0.8.0.9335/src/contour/session/TerminalSession.cpp#L960-L992)). --- This is the Markdown version of . On that page every validation case runs live in libghostty-vt, the terminal emulation core of Ghostty, compiled to WebAssembly.