Using the tus upload approach, developers who are building client-side applications or integrating uploads onto their own websites or services can use metadata returned by the API to generate upload progress bars.
To generate an upload progress bar with the tus upload approach, you’ll need to make periodic HEAD requests to the upload_link.
Learn more at 'Working with Video Uploads' on our Vimeo Developer Page.
Comparing the Upload-Offset (the amount of data on our upload servers) to the Upload-Length (the size of the file you specified) will give you the information needed to build a progress bar.