Thumbnail Size Checker
Drop a thumbnail image to check its pixel size, aspect ratio and format — locally, without uploading it.
How this tool works
- 1Select an image file from your device.
- 2The checker reads its width, height, ratio, file type and size in the browser.
- 3Compare the result with the recommended 16:9 and 1280×720 baseline, then preview it.
Limits and honest notes
The recommendation reflects common upload guidance at the time of writing. YouTube may change accepted limits. The file is read locally and is never sent to this site.