What Is an SRT File? Subtitle Files Explained

An SRT file is a plain-text subtitle file that lists each caption with a number, a start and end time, and the words to display. Video players and platforms like YouTube read it and show the text on top of the video at the right moments, which is why SRT is the most widely supported subtitle format. You can open and edit one in any text editor.

SRT stands for SubRip Subtitle, named after an old program called SubRip that extracted subtitles from video. The program is long forgotten; the format it used is everywhere.

Anatomy of an SRT file

Here's a short SRT file in full:

1
00:00:00,000 --> 00:00:02,400
Most people light their videos wrong.

2
00:00:02,400 --> 00:00:05,100
Here's the fix that costs nothing.

3
00:00:05,600 --> 00:00:08,900
Turn your desk so the window
is in front of you.

Each caption is a block with four parts:

1. Sequence number. Counts up from 1. Players mostly ignore it, but some tools complain if it's missing or out of order.
2. Timing line. Start time, the arrow -->, end time. The format is hours:minutes:seconds,milliseconds. Note the comma before the milliseconds; that detail trips people up.
3. Text. One or two lines is the norm. Some players support basic tags like <i> for italics, but support is inconsistent, so keep it plain.
4. Blank line. Separates one caption from the next.

That's the whole format. No colors, no positions, no fonts. That simplicity is exactly why it's so portable.

How to create an SRT file

From an editor or caption tool

The easiest way. Most video editors and caption tools can transcribe your video and export the result as an SRT. Review the text before exporting; automatic transcription often gets names, numbers and jargon wrong.

From YouTube

If your video is on YouTube, its automatic captions (once corrected in YouTube Studio's Subtitles section) can be downloaded as a subtitle file and reused elsewhere. See how to add subtitles to a YouTube video for the steps.

By hand

For a short clip you can type one yourself in a text editor following the structure above. It's tedious for anything over a minute, but it's a good way to understand the format. Save it with a .srt extension and UTF-8 encoding.

Editing timing

The most common SRT problem isn't the words; it's timing.

• Everything is early or late by the same amount. This usually happens after you trimmed the start of the video. Use a subtitle editor's "shift all" feature to move every timestamp by the same offset. Free subtitle editors like Subtitle Edit and Aegisub can do this.
• Timing drifts more and more over the video. Usually a frame rate mismatch between the file the captions were made for and the final export. Re-generate captions from the final video rather than trying to stretch them.
• A caption flashes too quickly to read. Merge it with the next block, or extend its end time. As a rough guide, short captions need at least a second on screen to be readable.
• Overlapping times. If one caption's end time is after the next one's start, some players show both. Fix the end time.

Golden rule: make captions from the final cut. If you change the edit after creating the SRT, the timings no longer match.

Common SRT errors and quick fixes

• Upload rejected: usually a formatting slip, such as a period instead of a comma in a timestamp, a missing blank line between blocks, or stray text at the top of the file. Open it in a text editor and check the first few blocks.
• Strange characters like é instead of é: an encoding problem. Re-save the file as UTF-8.
• Captions show HTML tags as text: the player doesn't support formatting tags. Remove them.
• Lines too long on mobile: split long captions into two blocks. Shorter captions are easier to read on small screens.
• Wrong file loads in a media player: players match subtitle files by name, so the SRT must have exactly the same name as the video, apart from the extension.

SRT vs VTT vs burned-in captions

VTT is close enough to SRT that converting is easy: VTT files start with the line WEBVTT, use periods instead of commas in timestamps, and allow extra features like positioning. Many tools convert between them in one click.

Burned-in captions aren't a file at all; they're part of the picture. That makes them work everywhere, including platforms that don't accept caption files, but they can't be turned off, translated or corrected after export. Read open vs closed captions to decide which you need.

For short-form talking videos, burned-in captions are usually the practical choice. ShotFlick's Auto Caption adds them directly to the edited video, so there's no separate file to manage on platforms that ignore SRT.