Practical
Subtitles and Captions: SRT, VTT, Soft and Burned In
Which subtitle format to use, what the difference between soft and burned in really costs you, and why your captions sometimes vanish when a file is converted.
3 min read · Published 22 August 2026
Most people encounter subtitles as a file that either works or mysteriously does not. The choices behind that are simple once laid out, and getting them right the first time saves re-exporting an hour of video.
The two ways subtitles exist
Soft subtitles are a separate stream of text with timings. The player draws them over the picture, the viewer can turn them off, change the size, or pick another language. The picture data does not contain them.
Burned in subtitles, sometimes called hardsubs or open captions, are part of the picture. Every frame has the text painted onto it. They cannot be turned off, resized or translated, because they are no longer text at all.
| Soft | Burned in | |
|---|---|---|
| Can be turned off | Yes | No |
| Multiple languages | Yes, several streams | No, one per export |
| Readable by search engines | Yes | No |
| Survives conversion | Often lost | Always |
| Plays on any device | Depends on support | Always |
| Costs a re-encode | No | Yes |
The honest summary: soft is better in every way that matters until it is not supported, and then it is worthless. Which is why social platforms that autoplay muted are the one place burning in is clearly right.
The formats
SRT is the plainest thing that works: a number, a time range, the text, a blank line. It has no styling, no positioning, and it is supported by essentially everything. Its simplicity is the reason.
VTT is SRT with a header and support for styling and positioning, designed for the web. If your video plays in a browser, this is the one to use.
ASS and SSA carry full styling, fonts, positioning and effects. Used heavily for fan subtitling and anywhere typesetting matters. Support outside dedicated players is poor.
| Format | Use it for | Styling |
|---|---|---|
| SRT | Anything, when in doubt | None |
| VTT | Web video and HTML5 players | Basic |
| ASS/SSA | Typesetting and effects | Full |
| Embedded MOV text | MP4 files carrying their own subtitles | Minimal |
Why subtitles disappear during conversion
This is the common complaint and it has two causes worth telling apart.
The first is that the destination container does not accept the subtitle format. MKV takes almost anything. MP4 is far pickier and will silently drop an ASS stream rather than convert it.
The second is that the tool was only asked to handle video and audio. Many conversion presets do not mention subtitles at all, so the streams are simply not carried across. Nothing errors, because nothing went wrong from the tool's point of view.
If subtitles vanished in conversion, check what the output container actually supports before assuming the file is broken. Converting the subtitle stream to SRT during the conversion usually resolves it, at the cost of any styling.
Captions and subtitles are not the same word
Subtitles assume the viewer can hear and transcribe the dialogue. Captions assume the viewer cannot, and describe relevant sound as well: a door closing, music starting, who is speaking when it is not obvious.
The distinction matters for accessibility obligations and for anyone watching without sound. If you are producing captions, describe the audio, not only the words.
A workable default
- Write or generate an SRT, and keep it alongside the video as your master.
- For your own archive and for anywhere that supports it, ship soft subtitles. They cost nothing and stay editable.
- For social platforms and anywhere autoplaying muted, burn them in, and keep the SRT so you can redo it later.
- For web delivery, convert to VTT and reference it from the player.
- Check the output plays with subtitles before deleting the source. Silent dropping is the failure mode here.
Keeping the original SRT is the part people skip. Once subtitles are burned into a picture there is no route back to text, so the timed file is worth more than the export it produced.
Common questions
Should I burn subtitles in or keep them separate?
Keep them separate wherever the destination supports it, since soft subtitles can be turned off, restyled, translated and read by search engines. Burn them in for social platforms that autoplay without sound, and keep the source file either way.
Why did my subtitles disappear after converting?
Either the destination container does not accept that subtitle format, MP4 being much pickier than MKV, or the conversion was only asked to handle picture and sound. Neither produces an error, which is what makes it confusing.
SRT or VTT?
VTT for web players, SRT for everything else and whenever you are unsure. SRT has no styling at all, which is exactly why nothing refuses it.
What is the difference between subtitles and captions?
Subtitles transcribe the dialogue for someone who can hear. Captions also describe relevant sound, such as music or a door closing, for someone who cannot.