What is SRT File?
An SRT file is a plain-text subtitle format that pairs numbered caption blocks with start and end timecodes, and it is the format most video platforms accept for uploaded captions.
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Each block has four parts: a sequence number, a timecode line in HH:MM:SS,mmm --> HH:MM:SS,mmm form using a comma before the milliseconds, one or two lines of caption text, then a blank line. The format carries no styling or positioning, which is why it is so widely supported.
Keeping captions as a separate SRT rather than burning them into the picture means viewers can turn them off, platforms can index the text for search, and you can fix a misheard brand name by re-uploading one small file instead of re-rendering the video. That matters for YouTube, where the caption track is readable content.
A single block looks like this: the number 12, then 00:01:04,500 --> 00:01:07,120, then the line of dialogue. Keep each block to about two lines and no more than roughly 42 characters per line, and give it at least a second on screen so it can be read. Transcription tools export SRT directly; edit the text before upload, since automatic transcripts reliably mangle names and jargon.
Where SRT File shows up
You will meet SRT File most often while comparing transcription & captions - Descript, VEED, Kapwing, and Rev all deal with it, though not in the same way or at the same price.
Related terms: Burn-in Captions.