I have used this extension for 3 years on both Windows 7 (today) and Windows 10 (this week) with Opera 68 and now 69. It is 100% reliable in stopping HTML5 videos, many of which lack any way to pause. It works on yahoo.com. I also have Ghostery installed, which I think helps the 100% part. I don't understand why this excellent extension has a low rating. Perhaps those who find it not working have too many extensions installed - that's sometimes a bad thing. I have 5: Ghostery, Bulk URL Opener & Copy URLs (very reliable session control), this one, and Tab Suspender (Tab Unloader).