# Customizing the actions taken when clicking on links

kitty has support for terminal hyperlinks. These are generated by many terminal programs, such as `ls`, `gcc`, `systemd`, `mdcat`, etc. You can customize exactly what happens when clicking on these hyperlinks in kitty.

You can tell kitty to take arbitrarily many, complex actions when a link is clicked. Let us illustrate with some examples, first. Create the file `~/.config/kitty/open-actions.conf` with the following:

    # Open any image in the full kitty window by clicking on it
    protocol file
    mime image/*
    action launch --type=overlay kitty +kitten icat --hold ${FILE_PATH}

Now, run `ls --hyperlink=auto` in kitty and click on the filename of an image, holding down ``ctrl`+`shift``. It will be opened over the current window. Press any key to close it.

Each entry in `open-actions.conf` consists of one or more Matching criteria, such as `protocol` and `mime` and one or more `action` entries. In the example above kitty uses the launch action which can be used to run external programs. Entries are separated by blank lines.

Actions are very powerful, anything that you can map to a key combination in kitty.conf can be used as an action. You can specify more than one action per entry if you like, for example:

    # Tail a log file (*.log) in a new OS Window and reduce its font size
    protocol file
    ext log
    action launch --title ${FILE} --type=os-window tail -f ${FILE_PATH}
    action change_font_size current -2

In the action specification you can expand environment variables, as shown in the examples above. In addition to regular environment variables, there are some special variables, documented below:

`URL`

  The full URL being opened

`FILE_PATH`

  The path portion of the URL (unquoted)

`FILE`

  The file portion of the path of the URL (unquoted)

`FRAGMENT`

  The fragment (unquoted), if any of the URL or the empty string.

## Matching criteria

An entry in `open-actions.conf` must have one or more matching criteria. URLs that match all criteria for an entry will trigger that entries' actions. Processing stops at the first matching entry, so put more specific matching criteria at the start of the list. Entries in the file are separated by blank lines. The various available criteria are:

`protocol`

  A comma separated list of protocols, for example: `http, https`. If absent, there is no constraint on protocol

`url`

  A regular expression that must match against the entire (unquoted) URL

`fragment_matches`

  A regular expression that must match against the fragment (part after #) in the URL

`mime`

  A comma separated list of MIME types, for example: `text/*, image/*, application/pdf`. You can add MIME types to kitty by creating the `mime.types` in the kitty configuration directory. Useful if your system MIME database does not have definitions you need. This file is in the standard format of one definition per line, like: `text/plain rst md`.

`ext`

  A comma separated list of file extensions, for example: `jpeg, tar.gz`

`file`

  A shell glob pattern that must match the filename, for example: `image-??.png`