Pixels are only the first check
A correctly sized thumbnail can still be hard to understand. Inspect the small preview: is there one clear subject, enough contrast and readable text? This tool cannot predict click-through rate.
Useful Tools Lab · Local processing
Thumbnail inspection desk
Check the file, then judge the picture. See a readable checklist and small-view previews before you upload.
1. Choose type & device2. Inspect the file3. Test small-view clarity
A preview is not an upload
This is a local image check, not a connection to YouTube. Eligibility, account verification and content rules still apply. Use the linked official guidance before publishing.
Current YouTube guidance
Recommended video resolution: 3840 × 2160. Shorts: 2160 × 3840. Minimum video width: 640 pixels; minimum Shorts height: 640 pixels. Use 16:9 for video and 1:1 for podcast playlists.
Mobile upload: under 2 MB for video or 10 MB for podcasts. Desktop: under 50 MB for video, Shorts and podcasts. Custom Shorts thumbnail uploads currently use YouTube Studio on a computer and require account verification. No separate mobile Shorts file limit is stated.
Size checks do not prove that an image will get clicks or that YouTube will accept the upload. Video thumbnails can also depend on account verification and content rules.
YouTube official thumbnail guidance (checked 15 Oct 2026)