Captions are text representing spoken words, such as dialogue or narration, and other meaningful sounds in the video.
Captions are time-indexed and synchronised to appear on the video screen at the same time as the words are spoken.
If more than 1 person is speaking, the captions should identify who is speaking.
Here are 2 examples of videos with captions:
Captions are either ‘open’ (always on) or ‘closed’ (can be turned on and off).
Generally, it’s best to provide closed captions so that people can choose whether or not to turn on captions.
Sometimes, there’s a good reason for providing open captions — for example, a video at a trade show booth where audio is not permitted.
How captions make a video more accessible
Captions provide access to video content for people who:
- have a hearing impairment
- have an auditory processing disorder
- have a learning or intellectual disability
- are not fluent in the language spoken in the video and find that reading the captions while listening to the audio improves comprehension
- are in a noisy environment where they cannot hear the video properly
- are in a public environment, like a library, where they do not want to make any noise.
Captions are also helpful for developing literacy, both in children and adults.
Meeting the Web Accessibility Standard
When you provide captions for a pre-recorded video, you meet WCAG’s Success Criterion 1.2.2 Captions (Prerecorded).
When you provide captions for live video, you meet WCAG’s Success Criterion 1.2.4 Captions (Live).
Additional auditory information in captions
In addition to the spoken words in the video, captions should include any sounds or tones of voice that are meaningful in the video. These types of captions should be set in square brackets.
Examples of meaningful sounds
- [laughs], [sighs], [whistles]
- [window slams], [sound of explosion], [doorbell rings]
- [sarcastically] — used to indicate the tone of voice, if this is necessary to understand the meaning behind the words
- [overlapping speech] — used if people are talking over each other
- [inaudible] — used when speech is indiscernible or inaudible
- [background chatter], [birds singing], [silence] — used when there is a significant break in audio and nothing is spoken for a while
How to create closed captions
For a pre-recorded video to have closed captions, it needs to have a caption file.
A caption file is a text file that contains:
- the text of the spoken words
- descriptions of meaningful sounds — provided in lower case letters and set within square brackets
- timecodes for when each line of text should be displayed so that they appear at the same time as the sound occurs in the video.
The most common caption file format is SubRip (.srt).
You can use a free or paid-for service to generate a caption file for you.
If your video is hosted on YouTube.com you can create the caption file for free.
- Turn on automatic captioning.
- Check the autogenerated captions.
- Edit the captions to make sure that they accurately describe what is said and include the important sounds.
There are other free tools available, such as:
If you have your own video hosting service and custom video player, make sure they support captions.
If you prefer, you can pay a service to create the caption file for you.
These are some examples of services that provide video captioning:
- 3PlayMedia.com — (closed and open captioning)
- CaptionSync — (closed and open captioning)
- Rev — (closed and open captioning)
- VEED.IO — (closed and open captioning)
- Cielo24 — (closed captioning only).
Prices and features vary from service to service.
How to create open captions
To include open captions in your video, choose one of the following options.
- Create and import a secondary file into your video editing software before burning the captions into the video — this secondary file is known as a sidecar file and it needs to be in the appropriate format for your video editing software.
- Use professional video editing software to burn the text onto your video.
- If you’re not familiar with the above processes, use a paid-for video captioning service.
Live captioning for live videos
Live captioning is done in real-time by a trained stenographer using a special keyboard.
Testing your video’s captions
Check the captions by listening to the video while reading the captions, making sure that the words and all meaningful sounds are correctly captured as and when they occur in the video.