Tools for captioning online videos

Do you have a video you want to make accessible online? This article looks at some of the options for creating and sharing captioned videos, and compares a number of free do-it-yourself (DIY) captioning tools.

DIY captioning tools

All do-it-yourself captioning programs have certain common features:

  • A video player which links to the source of a particular video
  • An edit mode which allows you to create and correct captions
  • A method for syncing the captions to the video using its timecode (basically a counter which runs invisibly through a video, counting up the hours, minutes and seconds as it plays)
  • A review mode where you can watch the video with your captions before posting them

The following is not intended to be a comprehensive guide on how to use these online captioning tools (each has its own more detailed instructions and demo videos) but it will give you some idea of how they work and how easy they are to use.

YouTube's auto-caption service

If you own a video on YouTube, one way of getting it captioned is to use YouTube's auto-caption service. To do this, go into your account. Click on the 'CC' button at the bottom of the player and then click on 'transcribe audio'. The video will then go into a queue for captioning, which could take a day or more depending on its length.

The captions are produced using Google's speech recognition software and are therefore inaccurate (sometimes to the point of absurdity), so simply putting the auto-captions on will generally not make the video accessible for the Deaf and hearing impaired. However, if you're the video owner, you can download the file and make corrections to it.

If you have a transcript of your video, you can also upload it to YouTube, and speech recognition will be used to match the transcript to the video and thus create a caption file automatically. To do this, log into your account and go to the video to you have a transcript for. Click on the 'edit captions/subtitles' button, then click on 'add new captions or transcript' and upload the transcript text file. Note that your video will need to have reasonable quality audio for this function to work.

Amara (previously Universal Subtitles)

Previously called Universal Subtitles, Amara is an open-source, non-profit project of the Participatory Culture Foundation. It supports YouTube, HTML5, Vimeo and other players.

To start captioning a video, enter the 'create' section. This will ask you to first copy in the URL of the video.

The captioning process has three steps: writing the captions, syncing them and reviewing them. As you enter each step, a demo video appears which you can choose to play or not.

The video player is to the left of the screen. You can play and pause it by clicking on the green 'play/pause' button, or by pressing the tab key on your keyboard. You can also shift the video back eight seconds by clicking on the blue 'shift back eight seconds' button, or pressing the shift + tab keys on your keyboard.

You play the video, pausing it when necessary and typing the captions into the box below the player. After you complete each caption, press 'enter'. You can go back and edit captions after you create them.

To time the captions, go to the next stage, syncing. You play the video, and at the point where each caption should appear on screen, click on the purple 'Tap when the next subtitle should appear' button, or press the down 'arrow key' on your keyboard.

In the next stage, preview, you can watch the video with your captions playing on it. As you play the video, a timeline runs beneath it, with the captions also running along this, each caption in a separate box. To adjust the timing of a caption pause the video, click on either side of the caption's box, then drag it to the left or right depending on where you want it to start or finish. This is quite different to the timing methods used in other captioning tools, although it doesn't take long to get used to.

The chief drawback of the syncing system is that fact that, when creating captions, you don't have the option of indicating where a caption should end. (In other words unless rectified, the caption will just stay on the screen until replaced by the next caption.) This means that if there are a lot of gaps between captions in the video, you'll be spending a long time in the syncing stage dragging caption boxes around to open up spaces between them.

Once you have finished captioning your video, you submit it to Amara and it is posted on the site. You can send the URL to others, or embed it in your website. Volunteers are also able to translate your captions into other languages.


CaptionTube is YouTube's DIY captioning software. If you own a video on YouTube, you can create a caption file for it, then upload it to YouTube. CaptionTube also allows you to caption YouTube videos owned by others, but will need to email the caption file to the owner of the video for uploading to YouTube.

Before starting to use CaptionTube, you will need to create a Google account (or you can use your YouTube username and password). If you have a video on YouTube that you wish to caption, you can import it to CaptionTube by clicking on the 'Personal video' button.

Note: The first time you do this, you will be given a link to YouTube, where you will be asked to allow CaptionTube to access your videos.

CaptionTube has three modes: Timeline, List and Preview. In Timeline, the screen with your video appears to the left, with a section to the right where you can type your captions and add timings. Only the caption you are currently working on is visible. In List mode, the screen is smaller, and a list of all the captions you have created is to the right of it, which you can scroll through. You can create captions in both Timeline and List mode. You can also edit your captions in List mode, and make changes to start times and durations. Preview allows you to play the video with the captions running underneath it.

To create a caption, pause the video where you want it to start and click on the 'Add caption' button. The timecode on the video at that point will become the start time of the caption, and an automatic duration of 2 seconds will be assigned to it. (You can alter this by pausing the video where the caption should end and clicking on the button to the right of the duration box.) After typing each caption, save it, then click the 'Add caption' button again to create the next one.

CaptionTube, which is still in beta version, has a number of drawbacks. Changing the timecodes for a caption you have already created can be problematic. If, for example, you wish the caption to start slightly later, the logical thing to do would be to move the video to the point where you want it to start and capture the timecode. Doing this, however, invariably brings up a notice saying, "Caption duration too short. Captions cannot be less than or equal to 0 seconds", even though the caption is longer than that.

Worse, when Media Access Australia created some captions on CaptionTube and previewed them, at a certain point they began to hang on the screen with later captions overlapping them. There didn't seem to be anything wrong with the timecodes of the captions, and no amount of deleting them and creating new ones rectified the problem. Media Access Australia therefore cannot recommend CaptionTube as a captioning tool at the moment.


dotSUB allows you to upload a video you own to its website, add subtitles or captions to it, and make it public. Volunteers can then take the text of your subtitles or captions and translate it into other languages. While primarily a project that focuses on getting videos translated into as many languages as possible, it also provides a very easy-to-use captioning tool.

To start captioning, register with dotSUB. Click on the 'Upload Your Video' on the home page. You will then be asked various questions about the video, including whether you want it to be a public video or remain private.

When the video is uploaded, select the 'transcribe' option. The video is controlled by various keyboard commands. Ctrl + Shift + P will start the video playing. After typing the text of your caption, press Ctrl + Shift + down arrow, which will enter the caption's end time. Hit Enter to save the caption, and Ctrl + Shift + P to commence writing the next caption. If the next caption does not need to start immediately, let the video play until it does, then press Ctrl + Shift + up arrow, which will create a new start time.

Once you have finished creating the captions, mark the file as a complete transcription. If you have chosen to make the video public, it can then be viewed with captions by anyone on the dotSUB website, and the captions used as a basis for translation into other languages.


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