Overview: Text subtitle formats
Text subtitle formats combine cue timing with character content and format-specific presentation rules.
Text-based subtitles can carry anything from simple lines to detailed placement and styling. The common formats below define different cue structures and rendering expectations. A correct text extraction can therefore preserve the words while leaving another question about how the player interprets their appearance.
Text-based subtitles
Text-based subtitles store characters and timed presentation instructions that a renderer turns into visible glyphs.SubRip (SRT)
SRT stores numbered text cues with millisecond start and end timestamps separated into plain-text blocks.WebVTT
WebVTT defines UTF-8 timed text cues, presentation settings, and cue markup for web-oriented text tracks.SubStation Alpha (SSA)
SSA is a styled subtitle script format whose v4 sections describe reusable styles and timed dialogue events.Advanced SubStation Alpha (ASS)
ASS stores styled subtitle events with a script coordinate system, reusable styles, and local or timed override instructions.Timed Text Markup Language (TTML)
TTML uses XML to describe timed text, styles, regions, and the timing relationships of nested content.MP4 timed text (tx3g)
tx3g identifies a 3GPP timed-text sample entry whose container timing and text modifiers describe a subtitle track.SAMI
SAMI stores HTML-like synchronized caption blocks and can associate different language classes with the same media timing.MicroDVD subtitles
MicroDVD stores text cues using numbered frame boundaries, so their elapsed times depend on the associated frame rate.