libass/libass
Freelibass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format.
FreeFree tier
About libass/libass
libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. It is mostly compatible with VSFilter, the standard Windows subtitle renderer. The library is cross-platform and supports both Autotools and Meson build systems. It is open source under the permissive ISC license. The project is hosted on GitHub with the latest release 0.17.5. Contact and bug reports are managed via the GitHub issue tracker and an IRC channel.
Key Features
Portable subtitle renderer for ASS/SSA format
Mostly compatible with VSFilter
Cross-platform support
Supports Autotools and Meson build systems
Open source under ISC license
Actively maintained on GitHub
Pros & Cons
Pros
- Lightweight and portable library
- Cross-platform compatibility
- Active development with recent releases
- Permissive ISC license allows flexible use
- Standard for ASS/SSA subtitle rendering
Cons
- Requires programming integration; not a standalone tool
- Limited to ASS/SSA subtitle format (no SRT, VTT, etc.)
- Documentation may be minimal (community-driven)
Best For
Rendering ASS/SSA subtitles in media playersSubtitle processing in video transcoding pipelinesIntegration into applications requiring advanced subtitle rendering
FAQ
What is libass?
libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format.
How do I get libass?
You can download the latest release from GitHub releases (version 0.17.5 as of June 2026) or clone the source code from the GitHub repository.
How do I build libass?
libass offers two build systems: Autotools (preferred for development and distribution) and Meson (works well on Windows, supports MSVC and static-only builds).
What license is libass under?
libass is licensed under the ISC license, a permissive open-source license.
How can I report a bug or request a feature?
Use the GitHub issue tracker for bug reports and feature requests. The project also has an IRC channel at irc.libera.chat/#libass.