Subtitle file formats
Three formats cover almost everything in practice: SRT for general use and desktop players, VTT for web video, and ASS when styling and positioning matter. Everything else is either platform-specific — SBV for YouTube, TTML and SCC for broadcast — or legacy, like the frame-based MicroDVD .sub. All of them store timed text except VobSub, which stores images of subtitles.
Last reviewed 2026-09-07
The formats worth knowing
| Format | Extension | Stores | Where you meet it |
|---|---|---|---|
| SubRip | .srt | Timed plain text | The default everywhere: players, editors, translators |
| WebVTT | .vtt | Timed text, positioning, CSS | Web video — the only format HTML5 accepts |
| Advanced SubStation Alpha | .ass, .ssa | Styling, fonts, positioning, karaoke | Anime fansubs, typesetting-heavy work |
| SubViewer / YouTube | .sbv | Timed plain text | YouTube Studio caption downloads |
| MicroDVD | .sub | Frame-numbered text | Older releases; needs the video frame rate |
| VobSub | .sub + .idx | Bitmap images, not text | DVD rips — needs OCR to become text |
| Timed Text Markup | .ttml, .dfxp | XML with styling and regions | Broadcast and streaming delivery |
| Scenarist | .scc | CEA-608 caption data | US broadcast compliance |
How to choose
- •Anything is fine → SRT. It is the lowest common denominator and that is its strength.
- •It plays in a browser → VTT, because nothing else works.
- •Karaoke, signs, precise placement → ASS. SRT cannot express it and VTT only partly can.
- •A broadcaster or platform asked for a spec → follow it exactly; TTML and SCC exist because of contractual requirements, not preference.
What survives a conversion
Converting between text formats is safe for timings and text. What breaks is everything a simpler format cannot describe.
| Conversion | Kept | Lost |
|---|---|---|
| SRT → VTT | Everything | Nothing |
| VTT → SRT | Text, timings | Cue settings, STYLE, NOTE, regions |
| ASS → SRT | Text, timings | Styles, fonts, positioning, karaoke timing |
| SBV → SRT | Everything | Nothing |
| MicroDVD → SRT | Text, timings | Nothing — but the frame rate must be right or the whole file drifts |
| SRT → TXT | Text | All timing |
Free converters
These run entirely in your browser — the file is read locally and never uploaded.
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See all convertersQuestions
Which subtitle format should I use?+
SRT unless something forces otherwise. It is read by more software than any other format. Use VTT for web video, because HTML5 accepts nothing else, and ASS when you need styling or precise positioning.
What is the difference between .sub and .srt?+
SRT stores absolute timecodes as text. The .sub extension covers two unrelated things: MicroDVD, which stores frame numbers and therefore needs the video frame rate, and VobSub, which stores bitmap images of the subtitles and needs OCR to become text at all.
Can any subtitle format be converted to any other?+
Between text-based formats, yes, with the caveat that a simpler target format drops what it cannot express. Image-based subtitles such as VobSub are the exception — they need optical character recognition first.
Which format does YouTube accept?+
YouTube accepts SRT, VTT and its own SBV, and exports captions in all three from YouTube Studio.