SubToolbox

Subtitle Converter — SRT, VTT, ASS, SBV & Text

Convert between SRT, WebVTT, ASS, SBV and plain text. The file is parsed in your browser — nothing is uploaded.

Quick answer: Open or paste a subtitle file in any common format, pick the target format, and download the converted file — the parsing and writing happen entirely in your browser, so the file never leaves your device.

Drop a subtitle file here, or browse — it stays on your device

Core facts
ReadsSRT, WebVTT, ASS, SSA, TTML/DFXP, SBV, MicroDVD .sub
WritesSRT, WebVTT, ASS, SBV, plain text
PrivacyConversion runs in the browser — no upload, no server
Style tagsDropped when the target is SRT or SBV (they are plain-text formats)
ChecksOverlaps, inverted timings, reading speed (chars/sec), 42-char line width

What this tool does

A subtitle converter rewrites the same cues — a start time, an end time and some text — from one file format into another. The timing text differs (“00:00:01,000” in SRT versus “00:00:01.000” in WebVTT), the container differs (plain text versus XML), and the extras differ (ASS carries styles and karaoke tags; WebVTT carries positioning settings). Everything else travels: subtitle count, order, and each cue's duration are preserved exactly. This converter detects the format automatically, shows every cue in a table before you commit, and flags timing problems — overlapping cues, inverted intervals, text that flashes by faster than a viewer can read — so a conversion never silently breaks your file.

Common uses

  • A transcript or subtitle file from one app won't open in another — convert rather than re-type
  • HTML5 web players need WebVTT; DVD-era players and most editors want SRT
  • Aegisub karaoke files (ASS) need simplifying for YouTube upload
  • Premiere/Adobe DFXP exports need to become SRT for other tools
  • Old MicroDVD .sub files (frame-based) need converting with the right frame rate
  • Check a file's timings and reading speed before submitting it to a client

How the format is detected

The detector reads the file's shape, not its extension: a “WEBVTT” header means WebVTT; a “[Script Info]” section or “Dialogue:” lines mean ASS/SSA; an XML root of <tt> means TTML/DFXP; “{123}{456}text” means MicroDVD; a comma-separated “0:00:01.028,0:00:03.500” line means SBV; and a “00:00:01,000 --> 00:00:04,000” line means SRT. Renaming a file's extension never fools it — which is exactly what happens when an SRT is really a text file with a wrong extension.

What each format is for

SRT (SubRip) is the lingua franca: accepted by YouTube, VLC, Premiere, DaVinci Resolve and virtually every player. WebVTT is the W3C standard for the HTML5 <track> element, so it is what a web player actually loads. ASS/SSA is the Aegisub family format with full styling — common in fansubbing and karaoke. TTML/DFXP is the broadcast and streaming exchange format (Netflix deliveries use TTML profiles). SBV is YouTube's minimal format from its old caption system. MicroDVD .sub stores frame numbers rather than times, so converting it needs the video's frame rate.

Frequently Asked Questions

Which subtitle formats can be converted?
You can read SRT, WebVTT (.vtt), ASS and SSA, TTML and DFXP, YouTube's SBV, and frame-based MicroDVD .sub files. You can write SRT, WebVTT, ASS, SBV and plain text. That covers the formats used by YouTube, Premiere, Aegisub, VLC and most web players.
Is my subtitle file uploaded anywhere?
No. The file is read with the browser's own File API, parsed by JavaScript running on your device, and the converted file is assembled locally. Nothing is transmitted, stored or logged.
Will I lose styling when converting ASS to SRT?
Yes — and any converter will behave the same way. SRT and SBV are plain-text formats with no room for fonts, colours or karaoke tags, so those decorations are stripped. WebVTT keeps positioning, and ASS keeps everything; if styling matters, convert between VTT and ASS.
What are the reading-speed warnings?
Subtitles are usually considered comfortable up to roughly 20–21 characters per second, with at most two lines of 42 characters. The converter measures each cue and flags anything faster, so you can split or shorten it before publishing.
Does conversion change the timings?
Never. Cue start and end times are carried across unchanged. Timings only change when you deliberately use the resync or frame-rate tools.

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