YouTube Thumbnail Preview Tool

YouTube thumbnail requirements

From YouTube's help centre, custom thumbnails should:

• Use a 16:9 aspect ratio for regular videos (9:16 for Shorts, 1:1 for podcast playlists).
• Be at least 640 pixels wide. YouTube now recommends up to 3840×2160 for videos; 1280×720 remains the common working size.
• Be a JPG or PNG image.
• Stay under the size limit for how you upload: 2 MB from mobile, 50 MB from desktop.

Your account also needs to be verified before you can upload custom thumbnails.

Why preview at small sizes

Most people decide whether to click from a thumbnail that's a few centimetres wide — often smaller than your fingertip in the suggested-videos column. Details that look great full-screen in your editor disappear at that size. The two checks that catch most problems:

1. The squint test. Look at the tiny version. Can you still tell what the video is about? If not, simplify: fewer elements, bigger subject, less text.
2. The grayscale test. Turn on grayscale. If the subject doesn't separate from the background without colour, it won't stand out in a busy feed either.

Title and thumbnail work as a pair

Viewers read the thumbnail and title together. The best pairs don't repeat each other — the image shows the moment, the title adds the context or tension. More on that in the thumbnail best-practices guide, and you can score the title here too.

Frequently asked questions

What size should a YouTube thumbnail be?

16:9, at least 640 pixels wide. 1280×720 is the common working size; YouTube now accepts up to 3840×2160. Keep it under 2 MB if you upload from the mobile app, or under 50 MB from desktop.

Is my image uploaded anywhere?

No. The preview runs entirely in your browser. The image is never sent to our servers.

Why can’t I upload a custom thumbnail on YouTube?

Custom thumbnails require a verified YouTube account. Verify your account in YouTube Studio, then the option appears in each video’s details.