Subtitle formats explained: SRT, VTT, ASS, and where each one wins

Subtitle files are deceptively simple. At their core, they're just timestamped text: 'show this line of text from 00:01:23 to 00:01:25'. But the ecosystem has produced at least a dozen different formats — SRT, VTT, ASS, SSA, SBV, SUB, MicroDVD, TTML, SCC — and picking the right one for a given video player or platform requires understanding what each format adds beyond plain timestamped text.

This guide covers the formats that matter in 2026 and explains when to pick each.

SRT (SubRip Text)

SRT is the universal subtitle format. Almost every video player ever made reads SRT files. The structure is simple: a numbered cue, a timestamp range, and one or more lines of text, separated by blank lines. There's no styling, no positioning, no metadata — just text and time.

Use SRT when: you're delivering subtitles to a desktop video player (VLC, MPC-HC, mpv), embedding subtitles alongside an MKV or MP4 file for offline playback, sharing subtitles with someone whose player you don't know, or when you don't need any of the rich-text features that other formats offer. SRT is the lowest-common-denominator format and it's almost always the safe choice for non-web video.

SRT example

1
00:00:01,000 --> 00:00:04,000
First subtitle line

2
00:00:05,500 --> 00:00:08,000
Second line, with multiple
lines of text in one cue

VTT (WebVTT)

VTT is the web standard for subtitles. It was designed specifically for HTML5 <video> elements and is used by YouTube, Netflix, Vimeo, and most modern streaming platforms. VTT extends SRT with optional features: cue positioning, alignment, simple styling via CSS classes, region definitions, chapter markers, and metadata cues.

Use VTT when: you're delivering subtitles to a web video player (HTML5 video, YouTube, Vimeo, any streaming platform), or when you need basic positioning or styling beyond what SRT supports. VTT is essentially 'SRT plus web features' and most tools that read VTT also fall back to reading SRT cleanly.

Key differences from SRT

• Mandatory 'WEBVTT' header line at the top of the file.
• Cue numbering is optional (and usually omitted).
• Timestamps use periods before milliseconds (00:01:23.456) instead of SRT's commas.
• Optional position, alignment, and styling syntax appended to the timestamp line.
• Files must be UTF-8 encoded; SRT files in the wild are sometimes other encodings.

ASS / SSA (Advanced SubStation Alpha)

ASS (and its predecessor SSA) is the styled-subtitle format. It supports multiple text styles, custom fonts, colours, outlines, drop shadows, positioning, animation, and effects. It's the format used by anime fansubs and karaoke videos — anywhere subtitles need to look like more than plain timestamped text.

Use ASS when: you need karaoke-style subtitles with timing per syllable, animated subtitles, subtitles in multiple visual styles (different colours for different speakers, for example), or any subtitle treatment more elaborate than 'white text at the bottom'. The trade-off is that ASS is supported by a smaller set of players (VLC, MPC, mpv read it well; many web players don't).

ASS example

Dialogue: 0,0:00:01.00,0:00:04.00,Default,,0,0,0,,Hello world
Dialogue: 0,0:00:05.50,0:00:08.00,Title,,0,0,0,,{\c&H0000FF&}Red text

Niche formats worth knowing

SBV (YouTube)

YouTube's older subtitle format. Simpler than VTT (no positioning or styling), comparable in capability to SRT. Most platforms accept SRT or VTT now, so SBV is rarely the right export choice — but YouTube still accepts it for upload.

TTML (Timed Text Markup Language)

An XML-based subtitle format used in broadcast TV, Netflix's IMSC profile, and some enterprise video pipelines. Powerful but verbose; rarely the right choice for end-user video unless you're integrating with broadcast systems.

SCC (Scenarist Closed Captions)

The traditional closed-caption format for North American broadcast TV. Tightly bound to NTSC broadcast specs. If you're producing for traditional broadcast, you may need SCC; for everything else, ignore it.

MicroDVD (.sub)

A frame-based subtitle format from the late 1990s — timing is specified by frame number rather than millisecond. Mostly obsolete; if you encounter a .sub file from old archives, convert to SRT or VTT and modernise.

Choosing the right format: a flowchart

• HTML5 video / YouTube / web streaming? Use VTT.
• Desktop video player or sharing with non-technical users? Use SRT.
• Karaoke, anime fansub, or styled subtitles? Use ASS.
• Broadcast TV? You probably already know it's TTML or SCC.
• Anything else? Default to SRT — it's almost always accepted.

Encoding gotchas

SRT files in the wild are sometimes encoded in Windows-1252, Latin-1, or even region-specific encodings (Shift-JIS for Japanese, GB18030 for Chinese). VTT requires UTF-8. If you're converting an old SRT to VTT and the result has corrupted accented characters or missing non-Latin glyphs, the source SRT is in a non-UTF-8 encoding. Re-save the source as UTF-8 in a text editor first, then convert.

MegaConvert detects common source encodings automatically, but always sanity-check the result for any subtitles in non-Latin scripts before shipping.

Convert between subtitle formats

SRT to VTT, ASS to SRT, VTT to SRT, and any combination of the major subtitle formats — free, instant, no signup. Timing is preserved with millisecond precision; the format wrapper changes, the captions stay put.