Right size is the easy part. See how it holds up next to the real top videos on your topic in the Thumbnail Tester, check the words with the Thumbnail Text Checker, or study real thumbnail text from outlier videos.
Upload a 1280 × 720 image (16:9), as JPG, PNG or GIF, under 2 MB. That covers every screen. The harder part is making it readable when it's shown about as wide as your thumb.
It's YouTube's recommended resolution for custom thumbnails, with a 640-pixel minimum width. Designing larger and exporting at 1280 × 720 keeps text sharp on TVs.
A 800 × 600 screenshot, stretched
A 1280 × 720 canvas, exported as JPG
Any other shape is letterboxed with black bars in the player and feeds. Square images from other platforms need to be re-cropped, not squeezed.
A 1080 × 1080 Instagram post
The same photo re-cropped to 1280 × 720
In the phone feed and sidebar a thumbnail can be around 160–360 pixels wide. Big face, three words or fewer, strong contrast — and keep the bottom-right corner clear, where the video length sits.
Twelve words of small text across the bottom
Two large words top-left, face on the right
Rewrites are illustrative examples, not measured results.
1280 × 720 pixels, a 16:9 aspect ratio, with a minimum width of 640 pixels. Use JPG, PNG or GIF and keep the file under 2 MB.
Custom thumbnails need a verified YouTube account (phone verification in YouTube Studio). Check the file too: wrong format or an oversized file is the other common cause.
Export as JPG instead of PNG, or use the converter above: it exports a 1280 × 720 JPG and lowers quality step by step until the file is under 2 MB.
No. The check and the conversion run in your browser; the image never leaves your device.