SRT subtitle file
An SRT subtitle file (SubRip Subtitle) is a plain text file that stores subtitles as numbered lines with start and end timestamps. It is the most widely supported subtitle format across video editors, players and social platforms. An SRT file is unrelated to the SRT streaming protocol (Secure Reliable Transport), which sends live video over networks.
Why it matters
Subtitles widen reach to viewers who watch on mute, speak other languages or are deaf or hard of hearing. SRT is the format translation vendors and editing tools exchange most often. Supporting it makes it easy to add captions to a large library at low cost. A library can get captions without ordering a subtitle file per video: FastPix transcribes speech and generates subtitles through the API, at $0.048 per minute.
How it works
- Each subtitle is a numbered block in a plain text file.
- The block holds a start and end time in hours:minutes:seconds,milliseconds, joined by an arrow.
- The subtitle text follows on one or more lines, then a blank line ends the block.
- A player or platform reads the blocks and shows each line during its time range.
SRT vs WebVTT: which should I use?
Use WebVTT for web players and HLS streaming, and SRT for editing tools and exchanging files with vendors. The formats are similar, but WebVTT adds styling and positioning and is the native format for HTML5 video. Converting SRT to WebVTT is simple and lossless for basic text.
How do I add an SRT file to a video?
You add an SRT file either as a separate subtitle track or by burning it into the picture. Most platforms and players let you upload the SRT next to the video so viewers can turn captions on or off. Burning in makes captions permanent but cannot be switched off.
Is an SRT file the same as the SRT protocol?
No, an SRT subtitle file and the SRT streaming protocol share initials but are unrelated. The subtitle file is SubRip text. The protocol, Secure Reliable Transport, sends live video across the internet with error recovery. Check which one a tool means before uploading or configuring anything.
Where it's used
Creator apps, online learning platforms and OTT services use SRT files to add subtitles to videos, often supplied by translation vendors or AI transcription tools, so viewers can follow without sound.
Where it usually goes wrong, and how FastPix handles it
Writing or ordering subtitle files for every video is slow and costly, so many libraries ship without captions. That leaves out muted viewers, other-language audiences and viewers with hearing loss.
Generated subtitles from FastPix support multiple language tracks, and live streams can carry real-time captions, so muted viewers and viewers with hearing loss are covered at launch instead of after a vendor delivers.
By the numbers
- SRT timestamps use the format hours:minutes:seconds,milliseconds, with a comma as the decimal separator, as in 00:00:00,000. (SubRip (Wikipedia))
