What is an SRT file?
An SRT file (SubRip Subtitle file, extension .srt) is a plain-text subtitle file that stores subtitle cues: the timing information and dialogue that video players use to display captions over a video. Introduced by the SubRip software in the early 2000s, SRT remains the most widely supported subtitle format in the world.
Structure of an SRT file
Each SRT cue has three parts:
- A cue number on its own line.
- A timestamp range specifying when the cue appears and disappears.
- One or more dialogue lines.
Cues are separated by a single blank line. The entire file is plain text with no header, no metadata and no styling rules.
1 00:00:01,000 --> 00:00:04,000 Hello and welcome. 2 00:00:05,500 --> 00:00:08,750 This is a subtitle file. 3 00:00:09,000 --> 00:00:12,000 It stores timings and dialogue.
Timestamp format
SRT timestamps use the format HH:MM:SS,mmm — hours, minutes, seconds and milliseconds separated by a comma.
For example, 00:01:23,456 means 1 minute, 23 seconds and 456 milliseconds. The comma separator is important: WebVTT uses a period instead, and mixing the two is a common source of "invalid subtitle file" errors.
What tools open SRT files?
SRT is supported by nearly every video tool:
- VLC, MPC-HC, mpv, PotPlayer and most desktop video players.
- YouTube (SRT uploads are converted to YouTube captions automatically).
- Premiere Pro, Final Cut Pro, DaVinci Resolve, Avid Media Composer.
- Aegisub, Subtitle Edit, Subtitle Workshop and other subtitle editors.
- Any plain text editor for manual editing.
What can go wrong
SRT files are simple, but they can still fail. Common problems:
- BOM characters. Some text editors save files with a UTF-8 BOM, which a few players reject. Use the Encoding Cleaner to remove it.
- Mismatched millisecond separator. Commas work in SRT; periods are for VTT.
- Missing blank lines between cues. Players merge cues or fail to parse the file.
- Wrong encoding. Files saved as Windows-1252 instead of UTF-8 often display garbled characters.
- Cues not in chronological order. Some players handle this, others do not.
- Overlapping cues. Technically allowed by SRT but often a sign of bad timing.
SRT vs other formats
SRT is simpler than ASS, SSA or WebVTT but also more compatible. If you need styling or precise positioning, use ASS or VTT. If you need to make sure your subtitle works everywhere, use SRT.
See the SRT vs VTT comparison for a full breakdown of the two most popular formats.
Working with SRT files
This site has 25 free tools for working with SRT files — converting, shifting, validating, cleaning and analysing. Start with the full tool directory, or jump to the most-used tools: