SRT vs VTT vs ASS: Which Subtitle Format Should You Use?

The short answer

• SRT — choose it when you want the file to work everywhere. It is plain text, easy to edit and understood by virtually every player, TV and editor.
• WebVTT (VTT) — choose it for websites and HTML5 video. It is the only format browsers understand natively and it supports positioning and CSS styling.
• ASS / SSA — choose it when you need full control of fonts, colours, positions and effects, for example for anime or stylised videos, and your players are computers or phones with a capable app.

SRT (SubRip)

SRT came from the SubRip program that extracted DVD subtitles in the early 2000s. It has no official standard, which is one reason there are many small variations, but the structure is always the same: a number, a time line, one or more lines of text and a blank line.

1
00:00:01,000 --> 00:00:03,500
Hello, and welcome.

Strengths: universal support, tiny files, readable in Notepad, easy to fix by hand. Weaknesses: no defined styling (tags like <i> are common but informal), no positioning, no metadata, and no official encoding — files saved in legacy encodings cause the classic garbled-character problem described in our encoding guide.

WebVTT (VTT)

WebVTT was designed by the W3C for the web. A file starts with WEBVTT, uses a dot instead of a comma in time stamps, and supports cue settings (position, line, alignment, size), regions, comments and CSS styling through the ::cue selector. The HTML <track> element reads it directly, and streaming protocols such as HLS carry subtitles as WebVTT segments.

Strengths: native in browsers, UTF-8 by definition, stylable, supports speakers and language spans. Weaknesses: support in older TVs and hardware players is patchy, and styling can look different across browsers.

ASS / SSA (Advanced SubStation Alpha)

ASS is a script-like format used in fansubbing and by the Aegisub editor. Each line has a style (font, size, colours, outline, shadow, margins) and optional override tags for rotation, movement, fades, karaoke and even vector drawings. The rendering engine libass is built into VLC, mpv, Kodi and many Android and iOS players.

Strengths: unmatched typographic control, consistent appearance, effects. Weaknesses: large and complex, poorly supported by TVs and set-top boxes, fonts are not embedded in the file, and converting to anything else loses the styling.

Feature comparison

Which format for which job?

• Uploading to a video platform: SRT or VTT — both are accepted widely.
• Your own website: VTT, because of the <track> element. See how to add subtitles to HTML5 video.
• Playing on a TV or media box: SRT.
• Anime, karaoke or styled titles: ASS, with SRT as a fallback.
• Archiving: keep the format you received plus an SRT copy.

Converting safely

Converting up the ladder (SRT → VTT → ASS) is always safe because nothing needs to be invented. Converting down (ASS → SRT) discards styles, positions and effects; the text and timing stay. Use the SRT to VTT, VTT to SRT, ASS to SRT and SRT to ASS converters — they run in your browser, so the files never leave your computer.

Other formats you may meet

• SBV – YouTube’s simple caption export; see SBV to SRT.
• MicroDVD / SubViewer (.sub) – frame-based text subtitles; see SUB to SRT. The same extension is also used for image-based VobSub files.
• LRC – synchronised lyrics for music players; see LRC to SRT.
• TTML / DFXP, SCC, STL – broadcast and OTT delivery formats used by professionals. They are XML or binary and usually need specialist software.

For everyday work, mastering SRT, VTT and ASS gets you through nearly every situation. When in doubt, keep an SRT copy: it is the format that every other format can be created from with the least friction.

Frequently asked questions