In-Depth Look At YouTube Closed Captions – YouTube SEO and More

In-Depth Look At YouTube Closed Captions – YouTube SEO and More

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A few weeks back, I mentioned that YouTube and Google were indexing YouTube’s closed captions and subtitles. In fact, YES – both Google and YouTube ARE indexing videos for text that is contained within closed captions and subtitles. In this post, I would like show you why you should be taking advantage of YouTube’s closed captions feature for SEO, amongst other compelling reasons. Get ready, cause this is a really long one… If you dont want to read the whole post, skip to my video below.

Closed Captions, Speech-to-text, and Indexing Video Content

At we’ve talked for a couple years about various issues that exist with regard to search engines crawling and understanding online video content. We’ve also talked a bit about the testing of and usage of advanced recognition technologies to assist search engines it terms of attributing accurate, direct temporal metadata to multimedia content so as to better digest, index, categorize, and rank that content.

Direct temporal metadata, simply put, is time-based metadata that is related to the essence of the media content. Speech recognition analysis performed on audio or video content is one method that can be used to produce temporal metadata (e.g. timed-text, closed captions), which can assist search engines towards better “understanding” and cataloging multimedia content. Closed captions are more than just text displayed on the bottom of a screen to represent the dialog of a video. They can also include environmental sounds like birds singing, phones ringing, people knocking on doors, etc. They can include a note about when music is being played, where the scene is, when there is laughter and who is speaking.

Several companies have successfully deployed speech-to-text analysis models for use in online video. RAMP (formerly Everyzing) is one company that we’ve talked about in the past that uses patented speech-to-text recognition technology to extract textual meaning from multimedia content that contains spoken word. Their customers have seen first hand the benefits of using extracted temporal metadata for SEO. Blinkxand Truveo, both video search engines, have stated that they use speech-to-text recognition to help catalog video content. After all, the goal of a video search engine is to process as much information as possible to enable accurate and relevant search results – the audio track of a video is one piece of information that can be incredibly valuable to that affect.

Google’s Focus on Closed Captions, Speech-to-text & Search

Google has also been hard at work at refining speech-to-text models for extracting temporal metadata within video. We’ve covered Google’s attempts at building, refining, and launching solutions for speech-to-text analysis.

Apr. 2007 – Google 411. Google launched a great free 411 call information service (you should try it, I use it all the time) whereby users can call 800-GOOG-411 to get free, automated directory assistance. Google stated publicly that their intentions for launching the service were entirely related to building a speech-to-text model that could be leveraged for better video search.

“Whether or not free-411 is a profitable business unto itself is yet to be seen… The reason we really did it is because we need to build a great speech-to-text model … that we can use for all kinds of different things, including video search.” – Google’s Marissa Mayer

Sept. 2008 – GAudio launches with YouTube speech-to-text for political campaigns. This has since been removed by Google but this was their first publicly available functionality to allow users to search through video content, in this case video content related to the 2008 presidential campaigns, based off words spoken within the videos.

Nov. 2009 – Google Rolls out automated YouTube closed captions (limited)

Mar. 2010 – Automated captioning for all videos (Beta – English only). Just as I predicted for 2010, YouTube rolled out machine automated closed captioning for YouTube videos using Google’s speech-to-text recognition capabilities. As a result, it is now incredibly easy for YouTubers to upload a plain text transcript and have it automatically formatted into a closed captions file that works with the YouTube video.

PROOF – YouTube’s Closed Captions DO Work for Video SEO

So, it probably comes as no surprise that YouTube and Google ARE, in fact, using the text within closed captions on YouTube to index YouTube videos.

Back in October of 2009, Mike Lees, a ReelSEO reader and Founder of, emailed me to show results whereby his videos were being ranked for terms only found within his closed captions and subtitles on YouTube. According to Mike, for his videos, he has seen views on some of his videos increase 10 fold after the addition of closed captions. While Ive known about this for many months now, I was unable to duplicate results myself until earlier this year. As a result of this discussion with Mike, I set out to do several tests to prove that YouTube was indexing the text from closed captions files. So, it has taken me close to 4 months to get this post up, but better late than never, right?

The following is a video I created to demonstrate proof that YouTube and Google are indexing videos for the text contained within closed captions on YouTube:

Notes and Observations:

I thought it might be worthwhile to mention several items I found in my tests.

  • First off, I think that it is interesting that in the example test here, the video was not indexed for “RSEOKW9”, which is included within the comments on the video. I will need to do more research here but it appears that perhaps the content of the comments on YouTube is not being used for indexing videos. Of course, most YouTube comments are useless so perhaps this makes some sense.
  • Additionally, I find it interesting to note that YouTube is also not using the annotations. Of course, this makes some sense as annotations often are used to point to other videos and seldom contain useful information about the video being watched.

Transcripts vs. Closed Captions vs. Automated

  • For several of my YouTube videos, I noticed that indexing was not working on videos for which I had previously uploaded closed caption files. Initially, my thought was that it may be related to the format in which I uploaded those files (.srt). However, it is now my belief that YouTube was tinkering with this and it is possible that it was turned off/on at some point during the time that I uploaded my closed caption files (in late 2009.)
  • Since February, I have successfully been able to get indexed for text contained in uploaded closed caption files in any format. In other words, successful indexing was seen for closed captions uploaded in *.SRT (SubRip) and *.SUB (SubViewer) formats, as well as for a plain text transcript uploaded using YouTube’s machine transcription to time-code the text into closed captions. This is worked for older videos where I replaced the closed captions with a new file.
  • As to the question of whether or not Google or YouTube is indexing only closed captions that are turned on by the user or whether or not they are actually using their speech-to-text to automatically index keywords spoken within all Youtube videos, it appears that at this point, only closed captions that are turned on by the YouTube video owner are being used for indexing. I did a test here using a video with a unique phrase of 3 keywords (with no results found) spoken clearly in the video. For this particular video test, I did not upload a transcript or closed captions file. Instead, I checked to see if the video would be indexed for the words that were spoken regardless. Additionally, I did check to make certain that YouTube’s machine transcript was accurately picking up the 3 keywords. The test was unsuccessful so at this point, it does appear that both YouTube and Google Video search index and factor into rankings the keywords found in caption files but not (yet) the keywords said in videos without captions or transcripts. I.E. – this only works for closed captions that are enabled by the owner.

Implications for Video SEO & YouTube Optimization

There isn’t anything “groundbreaking” here, in the sense that one would expect Google and YouTube to use the text within closed caption files to index videos. However, it is always nice to know this for certain, and now we do.

As for rankings and weight, it is difficult to say at this point what weight might be applied to keywords found within closed captions. I did do a few tests whereby I uploaded a video with keywords stuffed in the closed captions file, and it did not appear to rank any higher for the keyword used. This was not a comprehensive test (few controls, sample size, etc…) so the results are anecdotal at best, but they lead me to believe that at this point, text contained within closed caption files does not seem to “trump” text found within the title, description, links, or tags. All that being said, it would not surprise me in the least if YouTube were to begin to place more weight on the existence of closed captions within videos. Additionally, it would not surprise me if they were to begin to use their speech-to-text algorithms to automatically index words spoken in all YouTube videos, regardless of whether a user enables closed captions or not.

At this point, we can safely assume that uploading captions files to YouTube, even when only using a text transcript, can helps videos rank for words that are contained within the closed captions. Closed captions act as yet another signal to the search engines to help them better understand the video content. Adding closed captions to YouTube videos may help with indexing and ranking for more long-tail keyword phrases. For more competitive keyword phrases, closed captions is just one of many factors that need to be considered as more of a holistic approach to optimizing YouTube videos. Of course, adding a transcript to the description field would accomplish much of the same, but there are many additonal compelling reasons why you should start using YouTube closed captions.

More Compelling Reasons for YouTube’s Closed Captions

Not only is it compelling that closed captions can help with SEO, but additionally, there are arguably more important reasons to deploy closed captions on your YouTube videos – namely, 1) accessibility for the hearing impaired, 2) global reach with regard to translations, and 3) advanced Search Filtering.


Adding closed captions to a video may be one way in which to get some additional traffic by making the video accessible to those without sound-capable PCs (e.g. many office workers) or those with hearing impairments. Common web accessibility guidelines indicate that captions should be synchronized, equivalent to that of the spoken word, and accessible to those who need it.

On Youtube, closed captions can be turned on by default for users that need it and earlier this year, YouTube launched interactive transcripts for videos that have closed captions whereby a user can actually read the text transcript, which is highlighted in time with the video (see image at right.)

Translations = Global Reach

One strategy in having your videos reach a wider audience is to include captions and subtitles in multiple languages with your video. Adding captions and subtitles to your videos not only make your video accessible to those with hearing impairments, but adding them in multiple languages can help to drive additional traffic from non-English speakers and international audiences. You can also upload your closed captions in your preferred language, and then allow users to translate the captions using Google translate, as seen in the picture to the right.

Advanced Search Filtering

Both Google and YouTube allow searchers to filter searches for videos that only have associated closed captions. If you want your videos to be found by those users, you will need to enable closed captions.

How to Create and Publish YouTube Closed Captions

This post is already long enough, so rather than provide a detailed guide on how to add closed captions to YouTube, I will instead point you to our article from November titled, “How to Add YouTube Closed Captions, Subtitles & Translations.” In the post, we list out several available tools and services that will help you with creating closed captions for your videos.

Here is a list of just a few:

  • DotSub – No fee, video subtitling site and service in a ‘wiki’ style. You can view, upload, transcribe and translate all right through the site.
  • SubPLYis a service that you can use to generate transcripts and closed captions for your video. Check out our review of Subply vs. manual transcription.

Perhaps the easiest way to do this today, is to leverage YouTube’s automated machine transcription feature which allows you to upload a plain-text transcript of the video (no time-coding necessary). If you have a script for your video, you can upload this and Google will match the words in the text file with the audio to create closed captions that are time-based. If you do not have a plain-text transcript, you can use one of the services listed here, or you can download YouTube’s machine transcription file, fix it for errors, and then re-upload that file to YouTube.

Conclusion – DO IT!

Either way, whether for SEO, accessibility, global reach, etc… I highly recommend that you start adding closed captions to your YouTube videos. Good luck with your video marketing efforts and as always, keep it “reel.”


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