Many video SEO experts will tell you to upload a captions file or transcript of your video because when you speak the keywords you want to rank for those words then show up in search and give you a higher probability of ranking for that keyword. Is that really true? There’s some problems with this theory, primarily that it’s too easy to game. Mark Robertson of ReelSEO and I agree that YouTube and Google use the captions file to understand the contents of the video, but the search algorithm does not highly favor videos with captions versus videos without them.
However, you SHOULD use captions and transcripts on your video because it helps increase the watch time of your video, which does directly influence how your video ranks in search. It’s not that caption files in and of themselves make your videos rank better, but the better user experience provided by having captions available may increase the amount of time people spend watching your videos.