# libass/libass

libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format.

Repository: https://github.com/libass/libass
Canonical: https://ross.abutalabs.com/products/libass
Language: C
License: ISC
License Family: permissive
Topics: substation-alpha, libass, c, subtitle-formats, subtitles, cross-platform, ass, ssa, subtitle-format, advanced-substation-alpha
Last push: 2026-08-22T23:07:34+00:00

## Health v2 (maintenance only)
Score: 85/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 99, release rhythm 58, longevity 100
- inputs: {"age_days": 4786, "days_push": 11, "days_rel": 70, "gap_med": 381, "n_releases_24m": 2}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1161, forks 247 (observed 2026-08-28T04:03:49.425060+00:00)

## What it is
libass is a portable C library that renders ASS/SSA (Advanced Substation Alpha) subtitles, mostly compatible with VSFilter. It is widely used by video players such as VLC, mpv, and ffmpeg to display styled subtitles.

## Use cases
- render ASS/SSA subtitles in a video player
- burn styled subtitles into video with ffmpeg
- add karaoke and animated subtitle effects to playback
- portably display advanced subtitle formatting across platforms
- replace VSFilter in a DirectShow or VapourSynth pipeline

## When to choose
- you need accurate, VSFilter-compatible ASS/SSA subtitle rendering
- you are building or extending a media player or transcoding tool
- you need a portable C library with cross-platform builds

## When to avoid
- you only need simple SRT subtitle rendering without styling
- you want a ready-made player rather than a rendering library

## Facets
- artifact type: library
- maturity: stable
- function: graphics, image-processing, parser
- domain: media, cross-platform
- platform: windows, cross-platform, cpp
- tags: subtitles, ass, ssa, subtitle-rendering, vsfilter-compatible, c-library, video, linux, macos

## Member repositories
- libass/libass (main) score 85

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:03:49.425060+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T06:31:43.023519+00:00, confidence not recorded.
  - readme: https://github.com/libass/libass (fetched 2026-08-28T04:03:49.425060+00:00, sha 88a5b96874ac)
- Data as of 2026-08-30T08:39:29.467469+00:00.