A few days ago Google's John Mueller said this:

We do try to understand when something is a duplicate and treat it appropriately. So we do that with textual content, webpages for example, we try to recognize if something is a duplicate and filter it out when we show it in search. We do it with images where we can and we do try to do that with video as well.

So if you go and host your video on a number of different services that doesn’t mean it is going to show up 5 times instead of once in the search results.

Link to the source

Question: How could Google identify if a video is really a duplicate?

If I upload the same video to Youtube, Vimeo and Dailymotion, it will get transcoded differently by each of these sites thus the videos will have different hashes...

  • 1
    I have a video editor. I can open videos of various file types. When I look at the timeline, I am looking at blocks of content that will render into a continuous stream of frames- one after another. I can take two videos and use one to correct drops and skips by essentially comparing the two. This is a frame by frame examination of the two videos. I can even access an API in my own code to do this. If I can do this, what can Google do with a much larger budget and much smarter people??
    – closetnoc
    Commented Jul 8, 2015 at 15:01
  • @closetnoc but if a source video is transcoded with different settings, framerate might also be slightly different. Or it something other from what you're saying?
    – CamSpy
    Commented Jul 9, 2015 at 5:23
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    The point is that videos are not mysterious files that cannot be examined programmatically. This ability has existed with Google for quite a few years. It was simply not a practical technology at the time in that it really did not lend to the bottom line in search. It may be that the technology is being paid attention to because the ability to use it to enhance search in some respect is more realistic.
    – closetnoc
    Commented Jul 9, 2015 at 6:13
  • @closetnoc so what would you suggest doing if i'd like to submit the same or similar video to a few sites?
    – CamSpy
    Commented Jul 9, 2015 at 7:42
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    Oh I have no idea. I would think you would treat your video as if it were text content. Post it on the site you want it to be associated with first and wait till it has been found before posting elsewhere.
    – closetnoc
    Commented Jul 9, 2015 at 13:56

2 Answers 2


There is a lot more to matching video than just comparing file hashes. Google developed and entire video matching system for YouTube called ContentID which checks every video uploaded against a library of copyrighted videos.

For a simple explanation, let's start with images. (Google does more than matching hashes there too.) Resizing/cropping any image, even by 1px, would provide a different file hash. So there are many techniques employed to determine similarity.

If the images are not the same size we would resize one to match the other. Then we would compare pixel-by-pixel. Of course most of the pixels will be slightly different, but they will be quite close. So if over the entire image, the average "difference" between the pixels is less than some threshold, the images are the same.

Expanding that for videos, we can repeat that process for several frames in a video, as well as snippets of audio.

Of course, Google's ContentID is far more advanced than my explanation, but hopefully it gives you a basic idea.

Further reading:


Try creating different versions of your video with differential sound, frame-rate and encoding for different websites that you are uploading to.

Google maps the timelines to the video frames much like how Shazam maps waveform to timeline (as a whole or clips) for audio.

  • How do you know?
    – CamSpy
    Commented Oct 6, 2015 at 7:21
  • @CamSpy - personal experience with campaigns over the years... :-)
    – masmrdrr
    Commented Oct 6, 2015 at 7:28
  • This does not answer the question, "How does Google know?"
    – Rob
    Commented Jan 3, 2016 at 14:40
  • @Rob, much like how Google indexes and categorizes websites, audio files, images (based on weight, dimension ratios and color balance), they also index AV files based on FR, length, audio waveform, upload format and type of encoding (codecs used). You can imagine if I've been through this much trouble in the past, editing the same file multiple times, the resources Google has in it's arsenal to stop this kind of thing. Their main goal is UNIQUE content on Search, they wouldn't be successful if the same video was uploaded to multiple destinations.
    – masmrdrr
    Commented Jan 15, 2016 at 12:30
  • I'm not asking you to explain anything for my sake. I'm saying your original response does not answer the question asked. Without looking, if you feel your response to me does answer the question, you should edit your answer and put that there.
    – Rob
    Commented Jan 15, 2016 at 13:24

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