# Free YouTube thumbnail tester: preview your thumbnail and title

> Preview your YouTube thumbnail and title next to other videos, at the sizes of the home feed, search results, sidebar and phone app, and check the image against YouTube's upload rules.

URL: https://cutfac.com/tools/youtube-thumbnail-tester  
Last updated: 2026-10-28  
Language: [한국어](https://cutfac.com/ko/tools/youtube-thumbnail-tester)

Drop in a thumbnail and type your title to see them the way viewers do: small, with a length badge in the corner, next to other videos. The image stays in your browser.

Runs in your browser. Nothing is uploaded.

## How to use it

1. **Add a thumbnail.** Drop a PNG or JPG. It's read in the browser and isn't uploaded.
2. **Type the title.** Enter the title, channel name and video length. Titles past two lines are cut off as on YouTube, and the counter shows the 100-character limit.
3. **Switch layouts.** Look at the home feed, search results, the up next sidebar and a phone, and read the upload check under the form.

## What to look for

The sidebar is the hardest test: there the thumbnail is about 168 pixels wide. If you can't read its text or tell what it shows at that size, viewers scrolling past can't either.

- The length badge sits on the bottom right corner in every layout, so keep faces and text out of it.
- Titles stop after two lines on the home feed, in search and in the sidebar. Put the words that matter first.
- Next to the grey stand-ins, check that the thumbnail stands out by its colours and shapes alone.

## YouTube's thumbnail rules

YouTube recommends 3840 × 2160 pixels at 16:9, at least 640 pixels wide, as a JPG or PNG. A thumbnail uploaded from a computer can be up to 50 MB; from the mobile app, 2 MB.

Custom thumbnails need a verified account. For a Short, the thumbnail is vertical instead: see the YouTube Shorts thumbnail guide.

## Sources

- [YouTube Help: Add custom thumbnails on YouTube](https://support.google.com/youtube/answer/72431)

## Questions

### Are these the exact sizes YouTube uses?

They're close to what YouTube shows in a desktop browser about 1440 pixels wide and on a phone. YouTube resizes its grid with the window, so the real sizes move a little.

### Why does my thumbnail have bars?

It isn't 16:9. YouTube shows a thumbnail in a 16:9 frame, so crop it to 16:9, for example 1920 × 1080 or 3840 × 2160.

### Does this test which thumbnail gets more clicks?

No. It shows how a thumbnail looks. To compare click-through rates on real viewers, use Test & Compare in YouTube Studio.

### Is my image uploaded?

No. The image is read in your browser and never leaves your computer.