I ran a thumbnail test on one of my videos. Two versions. Same words on both. The only change was the picture behind the text. One took 74.9%. The other took 25.1%. Nearly three to one. And I would have picked the wrong one. One thing to know about that number: YouTube scores watch time share, not clicks. So the winner isn't just the one more people clicked. It's the one that brought in people who stayed. This is free and it's already in your Studio. Content → your video → Thumbnail → Test & compare. You upload two, YouTube splits the traffic between them, and it tells you which one won. No tools. No cost. No guessing. Two days of doing nothing told me something I could have got wrong on my own. Got a thumbnail you're unsure about? Bring it to Idea Hour — Tuesdays and I'll go through it with you one to one.

@Adil Ka I have noticed that you have changed the name from Pi to YouTube SEO does that mean we are doing YouTube SEO from now onwards, and nothing Pi related ... I have read that you wanted to change the name and do a channel but I presumed that was about Pi's related stuff?