MPSub to WebVTT Converter
FileFlip converts MPSub to WebVTT entirely inside your browser, using FFmpeg compiled to WebAssembly. The file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. That means no file-size limit, no queue and no account.
How do I convert an MPSub file to WebVTT?#
- Drop your MPSub file onto the converter at the top of this page, or click it to pick one from your computer. You can add as many as you like.
- Leave the target set to WebVTT and the conversion starts on its own. FileFlip downloads 30.8 MB of WebAssembly the first time and nothing after that, then runs FFmpeg on your own machine.
- Save the WebVTT file. Your browser writes it straight to your downloads folder, because there was never a server holding it.
Does converting MPSub to WebVTT lose quality?#
No. Subtitle cues are text, and converting MPSub to WebVTT rewrites the same timings and the same lines in the target's syntax. Anything WebVTT has no syntax for, such as positioning or styling, is dropped rather than degraded.
Is it safe to convert MPSub files online?#
Yes, because nothing is uploaded. FileFlip converts MPSub files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What MPSub to WebVTT actually does to the file#
Converting MPSub to WebVTT runs on FFmpeg, downloads 30.8 MB of WebAssembly the first time and nothing after that, rewrites the cues as text in the target's syntax, keeps cue durations.
| Engine | FFmpeg |
|---|---|
| Conversion path | One step: MPSub → WebVTT |
| Downloaded to your browser | 30.8 MB, once, then cached by your browser |
| Quality | Text preserved, unsupported styling dropped |
| You get back | One file |
| Where it runs | In a background worker, so the page stays responsive |
What survives the conversion
| What is in the file | This conversion | Why |
|---|---|---|
| Cue durations | Kept | Carried through into the converted file. |
What is an MPSub file?#
An MPSub file is MPlayer's native subtitle script, opening with a FORMAT line that declares whether the lines that follow are timed in seconds or in frames, with each subtitle giving its gap since the previous line and its own duration rather than an absolute start and end time.
Recognize MPSub if it turns up as MPlayer's own subtitle export; there's little reason to author new subtitles in it outside that ecosystem.
Convert MPSub to SRT to get absolute, frame-rate-independent timecodes that any player can read.
What is a WebVTT file?#
A VTT file is a WebVTT text track: a WEBVTT header followed by timed cues, each with a start and end timecode and one or more lines of text, optionally carrying position, size and CSS-style settings that place and format the text on screen.
Use WebVTT for subtitles served to an HTML5 <video> element, where the browser reads the track natively and honors its cue positioning and styling.
Convert WebVTT to SRT when the destination is a player or device outside the browser that only expects plain, unpositioned captions.
MPSub to WebVTT questions people ask#
What is an MPSub file?
An MPSub file is MPlayer's own subtitle format, where each line is timed by its offset from the previous line's end and its own duration, rather than by an absolute start and end timecode. A FORMAT line at the top of the file declares whether those offsets are measured in seconds or in frames.
Does MPSub timing break if the video's frame rate changes?
It depends on how the file was authored. An MPSub file with FORMAT=TIME is timed in seconds and stays in sync at any frame rate, but one authored in frame mode times its offsets in frame counts and drifts out of sync the same way MicroDVD does when the frame rate changes.
Can I convert an MPSub file to another format?
An MPSub file can be read and converted into a format like SRT that uses absolute, frame-rate-independent timecodes. Producing MPSub as an output is uncommon, since it's a format MPlayer exports rather than one other tools generate.
What is a WebVTT file used for?
A WebVTT file supplies the captions or subtitles for an HTML5 video, loaded through the <track> element so the browser displays them without any extra plugin. It's the format browsers expect natively, the way SRT is the format most desktop players expect.