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libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. It is mostly compatible with VSFilter.

Get it

See GitHub releases for the latest release 0.17.1 (released 2023-02-26). See the changelog for a detailed list of changes.

Source code is available from our GitHub repository.


Please use the issue tracker to report bugs or feature requests.

We have an IRC channel, too. Talk to us on Note that we cannot be online all the time and we cannot answer IRC questions if you leave the channel. Even if you do not get an immediate response, keep your IRC client open, and we will eventually get back to you.

Related Links

The following projects/companies use libass:

Information about the ASS format:

Other ASS/SSA implementations: