Free Tools for Captioning YouTube Videos

We at the University of Washington are working toward documenting a workflow that would support student interns in adding captions to the university's growing collection of YouTube videos. There are now a dozen or more tools that support the authoring and editing of captions, and over the last couple of weeks I've been exploring several of them. This is a semi-organized set of notes based on my experience with each tool. If others have experiences with these products, please comment!

There are several captioning tools that were not included in the current review, such as MAGpie (Windows and Mac), SubTitle workshop (Windows only), MovCaptioner (Mac only, and not free), the UW-Madison's World Caption (Mac only), and CapScribe, an open source tool developed by the folks at the Adaptive Technology Resource Centre at the University of Toronto.

CapScribe is particularly interesting because it includes a feature that renders audio description using text-to-speech, which I think is an interesting idea worthy of consideration and testing. The desktop version is Mac only, but there is work underway on a web-based version (currently in alpha).

All of these tools produce caption files that can be uploaded to YouTube. However, they don't meet our needs for the current project because we're looking for tools that can work with YouTube files directly, given URLs as input. We're wanting to caption videos that originate in a variety of different formats from dozens of different units at the UW. Acquiring and managing these videos would add a significant amount of overhead to the project. We'd rather just generate a prioritized list of YouTube videos and start captioning. Each of the following tools has that ability:


dotSub is both a tool and a community, providing through its website the means by which people from all over the world can caption (subtitle) videos into various languages. It's the site that has partnered with TED on the TED Open Translation Project.

It accepts as input uploaded videos, or videos on the web, for which it specifically prompts for a direct URL to an FLV file but is able to resolve YouTube URLs. It has keyboard shortcuts that dramatically facilitate the transcription process, which are critical not only for accessibility but for efficiency (see Benchmarks, below). The keyboard shortcuts are conveniently displayed immediately beneath the player window for those who have difficulty committing such things to memory.

Screen capture of the dotSub editing page

The captions show up immediately after they've been entered, so the user can see real time results as they add and edit captions, which is an important feature and not one that's universally available across the products I tested.

One problem is that it doesn't support private videos, which would adversely affect a workflow in which videos were uploaded to YouTube but kept private until they had been captioned.

SubTitle Horse

SubTitle Horse wins the Cutest Logo Award (a child-like, hand-drawn sketch of a horse head). Also, like dotSub, it has an extensive set of shortcut keys available. These shortcuts keys are not as readily available as they are in dotSub, but they're a click away, in the Help menu. Unfortunately the entire application, including the help menu, is built in Flash without much regard for accessibility. As such the list of keyboard shortcuts (a) isn't accessible to screen reader users, and (b) can't be visible on the screen at the same time as the caption editor (it must be closed to resume work). Otherwise, the interface is simple, easy to understand, and provides a complete set of features for meeting my captioning needs.

Screen capture of the Subtitle Horse editing page

Unlike dotSub, SubTitle Horse is somehow able to view private videos. I'm not sure if that's a good thing, since it does so without my providing YouTube account information. For the private-until-captioned workflow though, it's a nice feature. Another nice feature is that the video player jumps to the relevant point in the video when you select a caption to edit. dotSub does not appear to have this same functionality.

The greatest weakness of Subtitle Horse may be that it's a single session application. You don't have to create an account, which means your previous work is not saved. The workaround is to export your captions, even if only partially complete, then import them again during your next session.


CaptionTube is the tool that does the best job of utilizing Google's YouTube Data API. It interfaces directly with users' YouTube accounts, so they can easily access and caption their videos. Unfortunately the interaction between YouTube and CaptionTube does not include being able to seamlessly apply the captions once they've been created. That requires exporting the caption file, then uploading it to YouTube in a separate process, just as it does with all the other tools.

Screen capture of the CaptionTube editing interface featuring a timeline of captions

As with all the other tools, users can play and caption other users' videos. The instructions prompt users to export the captions and email them to the owner, which I think is good advice.

CaptionTube provides a pair of primary user interfaces (UI's) to choose from: a caption editor with a timeline, and a list of captions. One of these UI's would surely be enough to satisfy most users, but I found both to be confusing and either buggy (meaning the application doesn't work) or unintuitive (meaning I couldn't figure out how to make the application work). The timeline may have potential but since I'm a mouse user with eyesight I expect certain functionality from timelines, like the ability to click and drag to expand or reposition captions on the timeline. Without that functionality, the timeline is purely presentational, and in my opinion more frustrating than useful.

The documentation is inconsistent in reporting the names of buttons and keyboard shorcuts, which ultimately has left me a bit puzzled. There are separate references on the Help page to an "In Time" button and an "End Time" button, which probably are not synonymous, but both are said to have the same keyboard shorcut. Furthermore, I could never get one of these buttons, the button I believe to be the "In Time" (or "Start Time"?) button, to work (I've clicked it in every conceivable situation, and 100% of the time CaptionTube has accused me of wrongdoing).

Also, according to the documentation, CaptionTube has keyboard shortcuts, but I was unable to get any of these to work. They all conflict with common browser or OS keystrokes. For example, Alt + space is supposed to toggle play/pause, but in Windows that combination opens the window's control menu. Clicking various places on the screen to be sure the application has focus prior to trying a documented keyboard shortcut has no effect.

CaptionTube also has a tendency to be slow. After entering a caption, the user must save that caption before going on to the next, and saving sometimes takes a while. I'm not sure whether the bottleneck is on the client or server, but the delays were so significant when I tried using this on a slightly slower laptop that the application was totally unusable, which would seem to argue that it's a client issue.

Another shortcoming of CaptionTube, when compared to both dotSub and Subtitle Horse, is that the captions aren't visible on the video while editing. They appear elsewhere in the editor (either on the timeline or in a list), and can be viewed later in Preview mode, but that just isn't the same as seeing the final product and being able to tweak the captions on the fly.


Before you start accusing TubeCaption of messing with Google's trade name (CaptionTube), you should know that TubeCaption came first. In fact, they've been around for years. Unfortunately I'm not entirely sure what their current status is, but I've included them here just in case they're still alive and well. Their website was working earlier this week, although it wasn't fully functional, but as I publish this blog post I'm seeing signs of trouble even on their home page:

Screen shot of TubeCaption home page, which says: We're sorry, but something went wrong

TubeCaption, like dotSub, is/was as much a community as a tool. Their tagline is "We want all web videos to have closed-captions through community efforts" and for a while the community was working hard toward attaining that goal. They could select a YouTube video, caption it, then publish the captioned version for viewing on the TubeCaption site. Their caption editor (called Captionizer) has a long list of attractive-sounding features, including many that I especially value as you may by now know:

  • A user-friendly interface
  • Live preview of captions as they're being edited
  • Keyboard shortcuts

The feature list doesn't include the ability to export, and I suspect that may be a feature resulting from TubeCaption's business model. The site motivates people to caption video by offering them a share of the Google Ad revenue, so of course they would prefer that people view captioned video from their own site rather than go elsewhere. I'm not sure of the legality of embedding YouTube videos for a profit, but I do know that if there's no export option, this is not a tool that will work for our current project at the UW.


Overstream is similar to dotSub, but I found it to be slower (I often found myself waiting after clicking a button), and most critically, it has no keyboard interface (see Benchmarks, below.) I played with it for a while but could never get beyond these issues. That's why this review is so stinkin' short.

vSync Bookmarklet

vSync is very simple. The user installs a browser plug-in (in either IE, Firefox, Chrome, or Safari) then visits a YouTube video page. Then, a click on the vSync icon on the browser's toolbar triggers a tool with which the user can enter and submit a transcript. There's nothing here in the way of a transcript editor, so creating the transcript either requires a lot of clicking to and fro to play, pause, and type; or it requires using another tool. Once the user has a transcript and submits it via the plug-in, vSync quickly and automatically converts it into captions and sends the user an email when finished. This process is similar to that of Automatic Sync Technologies (AST), but AST charges for the service, and vSync is free. Before jumping to conclusions though someone should compare the accuracy and quality of the two services.

Once the captions have been automatically generated from the transcript, vSync provides an editor that allows you to tweak them, and unlike CaptionTube it does display the edited captions live in the video player. The editor lacks a few important features (e.g., the ability to insert a new caption) and has a few minor bugs, but these could easily be addressed.

Also of note, vSync provide a handy Caption Converter, which is great if you already have files in one caption format and need to convert them to another format, including SCC (for adding captions to iTunes videos). Being able to convert captions was once more critical than it probably now is for adding captions to YouTube, since originally YouTube only supported captions in SubRip and SubViewer formats. They now support (unofficially) a much broader variety of caption formats, so conversion is less likely to be necessary. However, at my request the vSync folks recently added an offset feature, which is something we need at the UW. We had videos that were already captioned, but when these videos were added to YouTube a brief introductory clip was added to these videos for branding purposes, which meant the timestamps on the captions were no longer accurate. vSync's caption converter allows us to generate a new caption file with caption times adjusted accordingly.

Easy YouTube Caption Creator

This is one of many simple yet handy accessibility-related tools available from Accessify. It's not as feature-rich as any of the other tools described here, nor does it pretend to be.

It simply prompts the user for a link to a YouTube video and a transcript (with line breaks where captions should break). Once the user submits this information, the transcript is presented in a simple caption editor, waiting for the user to timestamp the captions. The user does this by playing the video (by pressing the editor's "Play" button, not the play button on the video player) and pressing the letter a every time they want the next caption to appear.

There are no additional editing tools beyond this, and as such this tool is not likely to meet our needs. However, this tool may be perfect for someone just wanting an easy-to-use interface for generating quick captions without much thought or effort.

Technical Support

All the tools described on this page are free, so it could be argued that you get what you pay for in terms of technical support. However, in some cases you get much more than you pay for. This may not be a fair comparison since I haven't had a need to seek support on each of these tools. However, I did seek support on four of them:

  • Subtitle Horse: fantastic! I discovered an isolated bug in the video player, contacted support about it using a link on their web site, and had received a live reply within seconds. A few email exchanges later, Bj√∂rn had found and fixed the problem.
  • vSync: Awesome! Not only did the vSync folks promptly fix bugs as we spotted them, but they also added an offset feature at our request, and did so within very short order.
  • Easy YouTube Caption Creator: Outstanding! I experienced a problem that turned out to be a user error, but nevertheless, Ian Lloyd of Accessify was there to help within seconds after I sent an email.
  • CaptionTube: Ummm... This unfortunately was the lone blemish in my pursuit of technical support. Google's support is offered though the captionTube Google Group, which only has 22 members, and none of the six messages posted since June 18 has received a reply, including my two. More active Google Groups can be very helpful, but this one is clearly not active and no longer seems to be monitored by anyone at Google.


While reviewing these caption tools, I conducted a test to identify how long it might take for someone like me, with above-average but not lightening-fast typing speed, to transcribe one minute of UW video. I also wanted to test my hypothesis that transcribing/captioning with keyboard shortcuts is significantly more efficient than doing so with mouse clicks.


I selected two UW videos of approximate equal length. Both dealt with the same subject matter (swine flu), and both were "talking head" videos featuring professors who spoke quickly and packed in a lot of content, but were easy to understand. I captioned the first minute of each of these videos, and measured how long it took to attain 100% accuracy and satisfactory synchronization. Prior to starting either test, I practiced with other videos in order to ensure that I was reasonably proficient with both tools.

I captioned the first video with dotSub, and used the available keyboard shortcuts extensively. I captioned the second video with Overstream, which has few if any keyboard shortcuts.

This was not a blind test, and I entered the experiment with a personal bias. However, I sincerely tried in both trials to do my best work and create accurate captions as quickly as possible. Cross my heart.


  • Time to caption one minute of video using keyboard shortcuts: 8 minutes
  • Time to caption one minute of video using mouse clicks: 10 minutes


There are many tools available for adding captions to videos! This is great to see. It may suggest that there is a growing demand for captioned video, and with so many products freely available it will hopefully increase the number of individuals and organizations who are actively captioning their videos.

As we at the UW continue to work on adding captions to our small corner of the online video world, I'll keep you posted on our progress. Stay tuned...

6 comments on “Free Tools for Captioning YouTube Videos

  1. Interesting that your shortest review is on Overstream, the only one I've found to be usable and flexible enough for me.

    I've got 346 videos captioned on overstream
    , plus a few on bubblePLY, (though most were removed and source urls can only be changed by a slow to respond tech support)a few on tubecaption (from before all the "oops" problems - their importer with automatic timing rocked). Tubecaption developers stopped responding to my emails a couple of years ago.

    Most bothered me because of their dependence on youtube video as a source, since youtube videos tend to me put up and taken down more often, leaving the work useless.

    Overstream allows me to fix the video source by changing the stream, and I get fewer problems using myspace or Dailymotion video sources.

    Based on your reviews, I might give DotSub another try.

  2. Thanks for your post.

    I've created captions with problems until I uploaded the file and played the video. The captions stacked up on one another and only disapeared halfway up the screen, regardless of the end time I put on each caption.

    Have you, or anyone else, run into this problem? I don't know if it's user error or a bug in the program.

    I tried to contact the Google group, but entrance into the group is still pending a week on.

    I'm tempted to try one of the other captioning resources you mentioned but am wary of having the same effect.


  3. @theemptypen I haven't encountered that specific problem, but I haven't tried using CaptionTube since I did this review. Is your YouTube video publicly available? If so, do you mind sharing the URL so we can see what you're describing?

    Also if you post a few lines of the caption file that CaptionTube produced that may help with troubleshooting.

  4. I'm was totally user error. Not sure how my brain misinterpreted "duration" as "end time," but it did. Now it works perfectly.

    I'd also say that this is a positive for CaptionTube. Since they save the captions all I had to do was edit the times instead of reentering everything.