What is an SRT file, and how is it different from VTT?

An SRT file is a plain text file that pairs each piece of caption or subtitle text with a start time and an end time. A VTT file, which is a WebVTT file, does the same job for the web. The two are close relatives: WebVTT was built on SRT, but it has its own header and its own timestamp punctuation. A file in one format may not open correctly in a tool that expects the other unless you convert it.

SRT is a numbered list of timed blocks

Each SRT entry is numbered, and the numbers run sequentially from 1 ¹. Each entry has a time range and the text, and a blank line separates the entries. The timecode puts a comma before the milliseconds, not a full stop ². A two-entry file looks like this:

1
00:00:01,000 --> 00:00:03,500
[Music playing]

2
00:00:03,600 --> 00:00:06,200
MARIA: The recording is ready.

SRT is the older and simpler of the two. It is the format most subtitles on the internet are in ³, and many editing tools export it.

WebVTT is SRT's successor for the web

The W3C says that the SRT file format was used as the basis for the WebVTT text track format ⁴. The specification says the main use for WebVTT is captioning or subtitling video content ⁵.

A WebVTT file begins with the word WEBVTT. The specification's sample caption file for an interview starts that way, followed by its first timed cue ⁶. Its timestamps put a full stop before the thousandths of a second ⁷.

The same caption in WebVTT looks like this:

WEBVTT

00:00:01.000 --> 00:00:03.500
[Music playing]

00:00:03.600 --> 00:00:06.200
MARIA: The recording is ready.

The timestamp punctuation can break a file

A wrong timestamp separator or a missing header can break a file, and the text itself does not need to change. An SRT file with full stops, or a WebVTT file without the WEBVTT header and with commas, may fail in a strict parser.

It depends on where the file goes

• A video platform or editor. Many accept SRT. A 2024 walkthrough shows a creator who exported captions from a corrected transcript in Premiere Pro as a separate SRT file for YouTube ⁸.
• A web page. Use WebVTT, and test the file in the browser you will use. A converter can change one format into the other, but a bad separator or line break can break the file.
• Both. If you need both, keep one source file and export each format from it. That way the timing and text stay the same.

What to do

1. Check what the destination accepts. Look at the upload or player documentation before you export.
2. Use SRT for uploads and desktop tools. Keep the comma in the timestamps.
3. Use WebVTT for a web player. Start the file with WEBVTT and use full stops in the timestamps.
4. Open the file in the player you will use. Check the timing and line breaks before you publish.

For the rest of the caption process, see the guide to captions and subtitles. The question captions vs subtitles explains which text belongs in the file. The SRT file entry and the WebVTT entry give the format in short form. For getting a transcript to start from, see how to use Whisper to transcribe audio.