Free tool · No signup
YouTube Thumbnail Size Checker
Pick your thumbnail file and instantly check its dimensions, aspect ratio, file size and format against YouTube's rules.
- 100% free
- No signup
- Runs in your browser
Step by step
How to use the Thumbnail Size Checker
Step 01
Choose the image you plan to upload as a thumbnail.
Step 02
We read its dimensions, ratio, size and format — in your browser, never on a server.
Step 03
Fix anything marked red or yellow, then upload to YouTube without surprises.
Understand your results
What the results mean
YouTube's rules: thumbnails should be 1280×720 (minimum 640px wide), in a 16:9 ratio, under 2 MB, as JPG, PNG, GIF or WebP. Anything over 2 MB is rejected outright; wrong ratios get padded with black bars or cropped in some placements.
Your image is checked entirely in your browser with the standard file and image APIs — it is never uploaded to us or anyone else.
FAQ
Frequently asked questions
What is the correct YouTube thumbnail size?
1280×720 pixels (16:9). The minimum width is 640 pixels, and the file must be under 2 MB.
What file formats does YouTube accept for thumbnails?
JPG, PNG, GIF and WebP. JPG usually gives the best quality-to-size balance for photos; PNG for graphics with text.
Why was my thumbnail rejected by YouTube?
The most common reasons: the file is over 2 MB, or the format isn't supported. This checker catches both before you upload.
Do you upload or keep my image?
No. The check runs completely in your browser. The image never leaves your device.
What happens if my thumbnail isn't 16:9?
YouTube shows it letterboxed (black bars) or cropped depending on placement, which usually looks unprofessional. Crop to 16:9 first.
What is the YouTube Shorts thumbnail size?
Shorts are vertical: 1080×1920 pixels (9:16). Note that Shorts thumbnails can only be set from the mobile app at upload time, or by editing the video's thumbnail on desktop after publishing.
What is the YouTube thumbnail ratio?
16:9 for normal videos — at 1280×720 that's exactly right. This checker verifies the ratio of any image you pick.
Is this tool free?
Yes, free with no account or extension.
Last updated November 4, 2026 · Reviewed by the channelpeeker team · How we calculate
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