Subtitle Converter

SRT, WebVTT, SBV and ASS side by side

All four formats are plain text files with a start time, an end time and the words to show. They differ in how the time is written, what else a file may hold and which styling a player understands. The converter reads each of them and writes the one you pick.

WebVTT is the only one of the four with a formal specification, the W3C WebVTT format. It writes a full stop before the milliseconds, makes the hours optional, and lets a file carry comments, styles and regions. SRT never got a formal spec: the Library of Congress describes it as a simple text format that is not well standardized, with a numeric counter, a time line with a comma before the milliseconds, the text and a blank line. SBV is the SubViewer layout that YouTube lists for caption uploads, with start and end on one line separated by a comma.

ASS (Advanced SubStation Alpha) and its older form SSA keep their cues as Dialogue lines in an [Events] section. The fields follow the Format line of that section, the times are written in hundredths of a second, and the text is the last field, so it may contain commas. There is no official spec online to link to; the converter follows the field order the Format line gives and reads override tags as documented by the Aegisub subtitle editor.

What changes when you convert

• Italic, bold and underline are kept between SRT, WebVTT and ASS. SBV has no markup, so these tags are removed when you convert to SBV.
• WebVTT extras: NOTE comments, STYLE and REGION blocks, cue settings such as line:0 and cue identifiers stay only when the target is WebVTT. Converting to SRT, SBV or ASS drops them, and the result tells you how many.
• Speakers: a WebVTT voice tag like <v Anna> becomes the Name field of an ASS line, and the Name field becomes a voice tag in WebVTT. SRT and SBV have no field for it, so the name is left out.
• ASS styling: positions, colors, fonts, karaoke timing and other override tags have no counterpart in the other formats and are removed. Vector drawings are skipped and Comment lines are left out.
• Order: the cues are written in order of their start time, because WebVTT requires start times that never go back. ASS files often list signs and dialogue in another order.
• Font and color tags from SRT files are removed. They are not part of the other formats, and the Library of Congress notes that how SRT formatting shows up depends on the player.

Messy files it reads anyway

Subtitle files pass through many programs, and many of them bend the rules. The converter reads:

• a byte order mark at the start, Windows line endings (CRLF) and old Mac line endings (CR);
• SRT time lines with a full stop instead of a comma, and fractions with one or two digits, which count as tenths and hundredths of a second;
• SRT files with missing blank lines between cues, and cue numbers that skip or repeat (the output is numbered again from 1);
• ASS-style tags like {\i1} or {\an8} inside SRT files;
• files in Windows-1252 instead of UTF-8, and UTF-16 files with a byte order mark.

Lines that sit outside any cue are ignored and counted. If the result says cues end before they start, open the file and check those times: the converter keeps them as they are.

Which format to upload where

For a web page with a <video> element, use WebVTT: the W3C spec says the format is intended for text tracks used with the HTML <track> element. For YouTube, the YouTube help page on caption files lists SRT, SBV and WebVTT among the supported formats, says that only basic versions of SRT and SBV files are supported without style markup, and that WebVTT styling is limited to <b>, <i> and <u>. Positioned, colored or animated text only survives in ASS.

Need to fix the timing too? The Subtitle Timing Shifter moves all cues or stretches them to fit another frame rate. For a plain transcript of the spoken words, use Subtitles to Text.

How to convert subtitles

1. 1Paste the subtitle text into the box, or drop one or more files on it. The format is detected from the content.
2. 2Pick the target format under To. The converted text appears below, with a list of anything that had to be left out.
3. 3Download the file, or the ZIP for several files, or copy the text.

Sources

• W3C, WebVTT: The Web Video Text Tracks Format: file structure, timestamps, cue settings, NOTE, STYLE and REGION blocks, cue text tags
• Library of Congress, SubRip Subtitle format (SRT): the four parts of a cue, the time code format, the note that SRT is not well standardized
• YouTube Help, supported subtitle and closed caption files: SBV time line and the limits of basic SRT, SBV and WebVTT support
• Matroska, Subtitles: SSA and ASS sections, Dialogue fields and times in hundredths of a second
• Aegisub manual, ASS override tags: override blocks, \N, \n and \h, \i, \b and \u

Related guide

• MP4 vs WebM vs MOV: Containers, Codecs and What to Export

Built by Tobias. Updated October 23, 2026.

Frequently asked questions