at the top of the message and clicking the button which appears. Such
deletions are local-only and the messages will reappear if the page
page is reloaded. Admin users may additionally choose to globally
delete a message from the chat record, which deletes it not only from
their own browser but also propagates the removal to all connected
clients the next time they poll for new messages.

### Audible Notifications

On platforms which support it, chat can optionally play an audio file
when a new message arrives from any user other than oneself. The sound
can be selected or disabled via the settings menu. The list of sounds
includes a small selection of sounds built in to the fossil binary and
new sound files may be added to a repository as unversioned content:
when the chat page is loaded, it includes a list of all unversioned
files named `alert-sounds/*.XYZ`, where `XYZ` is one of (`wav`, `mp3`,
`ogg`) case-insensitive.

For example, a Unix-style shell command like the following would
install all WAV files in a local directory to the list:

```
for i in *.wav; do fossil uv add "$i" --as "alert-sounds/$i"; done
```

The list of sound files is sorted client-side for display in the
selection list. The user's selection of audio file is persistent in
a given browser, but if the file is subsequently removed from the
server then the next time the chat page is reloaded the sound will
fall back to the first one in the selection list.

## Implementation Details

*You do not need to understand how Fossil chat works in order to use it.
But many developers prefer to know how their tools work.
This section is provided for the benefit of those curious developers.*

The [/chat](/help?cmd=/chat) webpage downloads a small amount of HTML