Can't upload VTT caption files

New Contributor

For the past month or so, I have been completely unable to upload .vtt captions files to videos hosted on SharePoint/SP Streams. Every time I try, I receive the following error:



At this point I've attempted to upload multiple caption files on multiple browsers (Edge, Firefox, Chrome, Safari), multiple computers, and two different organizational SharePoint instances - nothing works. Going without captions or using autogenerated (which are also not functioning correctly) isn't an option here either since we have to meet accessibility requirements that require specific caption formatting.

Is there anything that I (or my account permissions) could be doing to cause this, or is it a larger issue with SP Streams in general?

3 Replies
best response confirmed by BLayman (New Contributor)

@BLayman thanks for taking the time to share your feedback with us, we really value it.  Firstly, my apologies on you not being able to upload your VTT file, could I suggest one alternative before opening a support ticket?


Could you please search online for "VTT file validator" and open one of your choosing?  In the past I have used Live WebVTT Validator ( in which you take the content of your VTT and paste it directly in the edit box.  It would parse the file and output any potential errors.


The reason I'm suggesting this, is because we actually parse the file for errors prior to uploading the VTT file, but we don't expose those details in the UI.  Please let me know how it goes, and thank you again for feedback!

@RodrigoTarratsThis did it! Apparently the YouTube default .vtt export adds two lines to the beginning of the .vtt file that the Streams parser doesn't like, and it won't allow the upload (which is interesting since Streams Classic had no issue with that). For anyone else with this issue, your .vtt file needs to start with:


00:00:00.000 --> 00:00:02.164

and not

Kind: captions
Language: en-US

00:00:00.000 --> 00:00:02.164

@BLayman I'm so glad you're finally able to upload your VTTs!  I will share your feedback with the team in terms of our VTT parser, and potentially displaying the parser's output in the UI to give more context about the error.


Thanks again for posting and sharing, we love your feedback!