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Get Started with HTML Video Captions

Published Friday, June 14, 2019 — 4 minute read

Did you know you can add captions to <video> elements with a little HTML and a VTT file? I didn't know until today! It's really easy to do (so long as you format your VTT file correctly... shout out to Conlin Durbin for helping me find that error 😄). At a minimum, you need 3 files:

  1. Video, probably .mp4
  2. WebVTT, where the captions are
  3. HTML

Let's get started

The HTML

1<video width="100%" title="Puppy" controls>
2  <source src="Puppiness.mp4" type="video/mp4" />
3  <track src="transcript.vtt" label="English captions" default />
4</video>
5

This is the easiest step. You only need 3 elements. On the <video> element, make you sure you include the controls attribute. This will allow users to toggle captions or switch to a different langue, if applicable.

The <source> element should be your video. Specify its src and type attributes. The <track> element is for the .vtt file you'll create in the next step. There are multiple attributes to include here.

  • kind defaults to "subtitles", but if you specify it you must also include the srclang attribute.
  • label is the title of the track and will be displayed in the video controls menu where captions can be toggled.
  • default is included to set a track as enabled.

WebVTT

1WEBVTT
2
31
400:00:00.000 --> 00:00:01.000
5SAND? OM NOM
6
72
800:00:02.000 --> 00:00:04.000
9NO, BLEH
10
113
1200:00:04.000 --> 00:00:08.000
13LEASH! OM NOM
14
154
1600:00:08.000 --> 00:00:10.000
17GIVE IT
18
195
2000:00:10.000 --> 00:00:14.000
21IS MINE
22

The format for this file is very specific. You must include "WEBVTT" at the top of the file, and then there are sections with white space in between which are called "cues". In the example file I've attached above, the first line of each cue is called the identifier. The next line specifies the timing for the cue. Finally, we have the cue payload. This is where you include the content for each caption. You can do some styling here.

The final product

Here's a GIF preview of the captions I added to a video of a puppy playing on a sandy beach.

A puppy tries to pick up its leash, bite too much sand and spits it out, then successfully grabs its leash and tugs on it.

More resources

I wasn't able to find a ton of examples out there, but there are plenty of resources that get into the differences between subtitles and captions, styling abilities, and additional ways to accomplish the same thing as above but with different transcript formats or third-party libraries.

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