You may experience an error when attempting to upload an MKV file to Vimeo while using Safari as your browser. Apple has reported an error wherein MKV files cannot be selected upon upload; the file will be greyed out.
Here is a workaround if you need to use Safari to upload a MKV file to Vimeo:
- Right-click on the greyed-out file.
- Select Quick Look from the menu.
- After Quick Look has initiated, observe the Choose button. Once Quick Look is active, the Choose button should also become active.
- Use the active Choose button to upload the MKV file.