AUCTORY TOOLS
1 · Thumbnail
Drop your thumbnail here
JPG / PNG / WebP — or click to choose
Everything runs in your browser — the image never leaves your device.
2 · Checks
Resolution, file-size and 16:9 checks appear here after upload.
3 · A/B compare
Upload a second thumbnail (B)
Both versions render side by side in every mockup. Hover a card to zoom — the click test.
4 · Video details
5 · Display
50% simulates how small thumbnails really appear in the feed.
Upload a thumbnail to see the previews.

YouTube Thumbnail Tester — Free Thumbnail Preview Tool

Test your YouTube thumbnail before you publish: upload a JPG, PNG or WebP image and instantly see it in realistic mockups of the search results, the home-page grid, the suggested sidebar and the mobile feed — in dark and light mode. Free, no watermark, no sign-up, and your files never leave your device.

The tool also checks what YouTube cares about: the recommended 2560×1440 resolution, the 1280×720 minimum, the 2 MB file limit and the 16:9 aspect ratio. If your image is not 16:9, the previews show the exact cover-crop YouTube will apply. Upload a second version to A/B compare both thumbnails side by side, and use the 50% shrink simulation to judge readability at real feed size.

How to use

1

Upload your thumbnail (JPG, PNG or WebP). Optionally add a second version for an A/B comparison.

2

Type your video title, channel name, views line and duration badge, then switch between dark/light mode and the 50% shrink test.

3

Read the automatic size, weight and 16:9 checks, compare the mockups and pick the thumbnail that stands out.

FAQ

Is this YouTube thumbnail tester really free?

Yes. It is completely free, with no sign-up, no watermark and no limits. You can test as many thumbnails as you like.

Is my thumbnail uploaded to a server?

No. Your image never leaves your device — every preview is rendered locally in your browser, so it is private and instant.

What is the best YouTube thumbnail size?

YouTube requires at least 1280×720 pixels in 16:9 and a file under 2 MB in JPG, PNG or WebP. For maximum sharpness on large screens, 2560×1440 is the ideal upload size — this tool checks all of that automatically.

Why does my thumbnail look cropped in the preview?

YouTube displays thumbnails in a 16:9 box. If your image has a different aspect ratio, the edges are cropped. The previews here use the same cover-crop behavior, so you see exactly what will be cut off.

Can I compare two thumbnails (A/B test)?

Yes. Upload a second image and every mockup — home, search, sidebar and mobile — shows both versions side by side, so you can judge which one draws the eye at a glance.