YouTube thumbnail checker

YouTube thumbnail size and rules in 2026

YouTube raised its thumbnail spec in 2026. In March its help page moved the recommended size from 1280 × 720 to 3840 × 2160, and uploads from a computer can now be up to 50 MB instead of 2 MB. Here is what the help page says now.

Recommended size, videos

3840 × 2160 px16:9 aspect ratio

Recommended size, Shorts

2160 × 3840 px9:16 aspect ratio

Minimum size

640 pxwide for videos, tall for Shorts

Maximum file size

50 MB from a computer2 MB from the mobile app (10 MB for podcasts)

Formats

JPG or PNG

Podcast playlists

1:1 square

Source: YouTube Help, Add custom thumbnails, checked October 5, 2026. YouTube announced the 50 MB limit on October 30, 2025; the dated change history, from archived copies of the help page and the API changelog, is on our thumbnail and CTR statistics page.

Older guides still say 1280 × 720 and 2 MB

That was YouTube's guidance until March 2026, and a 1280 × 720 JPG still uploads. The difference now is headroom: a 4K file gives YouTube a sharper image for big screens such as TVs, and the 50 MB cap means you rarely have to crush a detailed design to fit. If you upload from your phone, the old 2 MB limit still applies there.

What the checker can't judge for you

Specs only get a thumbnail accepted. Whether people click is decided at small sizes, so use the squint test above: if the main words aren't readable at 168 pixels wide, cut words or make them bigger. Keep faces and text out of the bottom-right corner, where YouTube shows the video length, and flip to dark mode to check it there too.

Want a scored check with heatmaps and A/B tests? ThumbnailRank is Mark Studios' thumbnail analyzer. Want the thumbnail made for you? Mark designs them.