What is an SRT file?
An SRT file is a subtitle file saved as plain text. Each subtitle has a number, a start and end time, and the words, with a blank line before the next one. The name comes from SubRip, the free Windows program that made the format popular, and almost every video player, editor and video site reads it.
The SRT format, line by line
Open an SRT in Notepad and every subtitle looks like this: the number 1, then a time line such as 00:00:01,000 --> 00:00:03,500, then the words, then a blank line. Times are hours, minutes, seconds and milliseconds, with a comma before the milliseconds. That comma catches people out, because VTT, the web's version of the format, uses a dot. A line can also carry simple tags like <i> for italics, though not every player shows them.
How to open an SRT file
Any text editor opens it: Notepad on Windows, TextEdit on a Mac. If double-clicking asks which app to use, pick one of those. To read and fix it with the times laid out next to each line, drop it on the subtitle editor, which opens it in your browser.
How to watch a video with an SRT file
Give the SRT the same name as the video and keep them in the same folder, for example holiday.mp4 and holiday.srt. VLC, Plex and Kodi then load it by themselves. In VLC you can also drag the SRT onto the video while it plays. For subtitles that show everywhere, including phones and social apps that ignore subtitle files, burn them into the video.
How to edit an SRT file
A text editor is fine for fixing a typo, as long as you keep the layout: number, time line, words, blank line. For more than that, use a tool that keeps the structure for you. The subtitle editor handles wording, shift subtitle timing moves every line earlier or later, and clean up fixes files that arrived messy.
How to make an SRT file
Start from what you have. A video or recording with speech: MP4 to SRT transcribes it into timed subtitles. A transcript or script: TXT to SRT. A subtitle file in another format: convert it to SRT. You can also type one by hand in a text editor using the layout above and save it with the .srt extension.
SRT and the other subtitle formats
SRT is the plainest subtitle format and the most widely accepted. It holds words and times, with no screen positions or fonts. VTT is nearly the same and is what web pages need for the HTML5 video player (SRT to VTT). ASS holds full styling and is common for anime (ASS to SRT). When a player or upload form rejects a subtitle file, converting it to SRT is usually the fix.
Questions
What does SRT stand for?
It comes from SubRip, the program that first wrote the format, which is why the files are also called SubRip subtitle files.
How do I turn an SRT file into plain text?
Drop it on SRT to text. The numbers and timestamps go and the words stay, one subtitle per line.
Why are my SRT subtitles out of sync?
Either they start at the wrong moment or they drift further out as the video goes on, and each has its own fix. Subtitles out of sync? helps you tell which in about a minute.
Why does my SRT file show strange characters?
It was saved in an older text encoding and is being read as UTF-8. Fix subtitle encoding re-saves it as UTF-8.