- What size does a YouTube thumbnail need to be?
- 1280×720 pixels minimum, 16:9 ratio, under 2 MB, in JPG, GIF, PNG, or BMP. The checker measures all of these and tells you exactly which one fails.
- Is my uploaded image sent to a server?
- No. Uploaded images are analyzed entirely in your browser — nothing is uploaded, stored, or logged. If you paste a YouTube URL, the server fetches the already-public thumbnail so your browser can analyze it without CORS restrictions.
- Is this a YouTube thumbnail checker with AI scoring?
- No, and that's on purpose. Every check is a deterministic rule with a published threshold — resolution, ratio, size, format, contrast, and visual density — so results are consistent and free. For scored AI candidates, use a ThumbMuse strategy pack.
- Why does text legibility matter on thumbnails?
- Most viewers see your thumbnail at phone size, where small text disappears. Keep text under four words and tall enough to cover roughly an eighth of the image height. The text-room signal flags designs that are too busy for that.
- My thumbnail passes everything but clicks are still low. What now?
- Passing the technical checks only means YouTube will display it cleanly. What the image says — the concept, emotion, and title match — drives clicks. That's what a strategy pack plans before you generate.
- Does the checker work for videos without a custom thumbnail?
- It checks whatever YouTube currently serves. For videos using an auto-generated frame, the resolution and contrast results describe that frame — design your custom thumbnail, upload it above, and check that instead.
ThumbMuse is an independent tool and is not affiliated with YouTube. Requirements reflect YouTube's published thumbnail guidelines.