YouTube thumbnail format, aspect ratio and file size limit

By KunStudio Editorial · Updated 2026-10-04

YouTube's help page recommends image formats such as JPG or PNG for thumbnails. The file size limit is 2 MB for video thumbnails uploaded from mobile and 50 MB from a desktop. The aspect ratio is 16:9 for videos, 9:16 for Shorts and 1:1 for podcast playlists. Uploading needs a verified account.

File types

YouTube's help page says to upload custom thumbnails in image formats such as JPG or PNG. PNG keeps hard edges and text crisp but makes bigger files; JPG makes smaller files, which matters if you upload from a phone and need to stay under 2 MB.

File size limits depend on where you upload

This is why older advice of a flat 2 MB limit is only half right today: 2 MB applies to mobile uploads of video thumbnails.

Aspect ratio by content type

The sizes are covered in the thumbnail size guide and the Shorts thumbnail guide.

Why a thumbnail upload fails

The help page points to a handful of causes. Your account may not be verified, since custom thumbnails need a verified account. The file may be over the limit for the device you are using, which is 2 MB on mobile. The image may break the Community Guidelines (nudity, hate speech, violence, harmful content), which can get a thumbnail rejected and a strike issued. Or the channel may have hit the daily custom thumbnail limit; YouTube says to try again in 24 hours when you see the message "Daily custom thumbnail limit reached", and that limits vary by country or region and channel history.

A quick export routine

Pick the ratio for the content type. Export JPG or PNG. If the file is over your device's limit, switch PNG to JPG or upload from a desktop instead of shrinking the pixel size. Then upload in YouTube Studio and check the preview.