YouTube Thumbnail Preview & Tester
Compare up to three thumbnails where viewers will see them — before you upload.
Your thumbnails
Shown in the duration badge.
How they look on YouTube
Add a thumbnail to see it here. Sizes are the ones measured on YouTube; a smaller screen shows them scaled down.
About the YouTube Thumbnail Preview & Tester
Drop up to three thumbnail options and type your title and channel name to see them as viewers will: in YouTube’s home grid, search results, the suggested videos beside the player and the mobile feed, in YouTube’s light or dark theme. The cards copy YouTube’s layouts at the sizes measured on its website, with the duration badge in the corner and the title cut to two lines, so you can tell whether a face, a word or the main object still reads at the smallest size — and which option stands out.
Each image is checked against YouTube Help’s thumbnail specs: the 16:9 shape, at least 640 pixels wide (YouTube recommends as large as possible, 3840 × 2160), JPG or PNG, and the file size — 2 MB when you upload from a phone, 50 MB from a computer. Your images stay on your device.
How to use it
- Choose or drop up to three images (or paste one with Ctrl+V). They are labelled A, B and C.
- Type the title, your channel name and the video length for the duration badge.
- Switch between YouTube’s light and dark themes and compare the options in each layout.
- Read the checks under each image and fix what is flagged — crop to 16:9, or compress under 2 MB if you upload from a phone.
- Remove an option, or drop another image to replace it, until you have your winner.
Examples
1280 × 720 JPG, 380 KB
Shape 16:9 · Width over 640 · Under 2 MB
It can be uploaded from a phone or a computer. YouTube recommends going larger, up to 3840 × 2160, if your design allows.
1170 × 2532 PNG, 3.1 MB
Shape not 16:9 · over the 2 MB phone limit
Crop it to 16:9 and save it as JPG to get under 2 MB.
Common uses
- Picking the best of two or three thumbnail designs before you upload, or before you run YouTube’s own test.
- Checking that text and faces still read at the smallest size, beside the player.
- Seeing how a thumbnail looks against YouTube’s dark theme, which many viewers use.
- Showing a client or a team the options in context.
YouTube’s thumbnail specs
From YouTube Help, Add video thumbnails:
- “Your custom thumbnail image should be as large as possible”, with a resolution of 3840 × 2160 for videos and at least 640 pixels wide.
- An aspect ratio of 16:9 for videos (9:16 for Shorts, whose custom thumbnails can only be added in YouTube Studio on a computer).
- Image formats such as JPG or PNG.
- File size: 2 MB for video thumbnails uploaded from a phone, 50 MB from a computer.
- Your account must be verified to upload custom thumbnails, and there is a limit to how many a channel can upload each day.
On the home, Explore and Subscriptions pages, vertical videos with a 16:9 thumbnail get an automatic 4:5 one instead, the same page says.
The sizes in the previews
Measured on YouTube’s website: thumbnails are 420 × 236 px in the home grid of a 1920 × 1080 window (smaller in smaller windows), 500 × 281 in search results, and 360 × 203 on the mobile site of a 360-pixel-wide phone. Beside the player they vary the most — between 207 and 359 px wide in our measurements — so the preview uses the smallest. The duration badge is the same small label everywhere: white 12-pixel text on a dark box, 8 pixels from the bottom-right corner, so keep important details out of that corner.
When your screen is narrower than a layout, the preview is shrunk as a whole, so titles are still cut where they would be at full size.
What makes a thumbnail work small
- One clear subject — a face, an object, a result — big enough to read at 207 pixels wide.
- Few words, in large type with an outline or a dark band behind them; the title already says the rest.
- Strong contrast with both YouTube backgrounds: white in the light theme, near-black in the dark one.
- Nothing important in the bottom-right corner, under the duration badge.
- Follow YouTube’s Community Guidelines: thumbnails with nudity or sexually provocative content, hate speech, violence or harmful or dangerous content can be rejected and earn a strike, YouTube Help says.
Limitations
- The layouts copy YouTube’s cards at measured sizes; YouTube changes its design and runs layout tests, so real pages can differ slightly.
- Fonts differ by device (YouTube uses Roboto), so a title may be cut a word earlier or later.
- Up to three images at a time. Formats your browser cannot open (for example HEIC outside Safari) need converting first.
- This preview does not run a test with real viewers; YouTube Studio’s own thumbnail test does that after you upload.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
What size should a YouTube thumbnail be?
YouTube Help says 16:9, as large as possible — 3840 × 2160 — and at least 640 pixels wide, as a JPG or PNG. Keep it under 2 MB if you upload from the YouTube app on a phone; from a computer the limit is 50 MB.
Why does YouTube say my thumbnail is too big?
Uploads from a phone are limited to 2 MB. Save the image as a JPG (not PNG) or compress it — the Image Compressor can bring it under 2 MB — or upload it from a computer, where the limit is 50 MB.
Are my images uploaded?
No. They are shown from your device with your browser; nothing is sent to a server, and the page works offline once loaded.
Can I test thumbnails with real viewers?
Not here: this shows how they look. After you upload, YouTube Studio’s Test & compare can test up to three titles and thumbnails with real viewers — on a computer, for channels with advanced features — and shows everyone the one with the most watch time. Use this preview to choose which three to test.
Does the duration badge cover part of my thumbnail?
Yes: a small dark label with the video length sits in the bottom-right corner everywhere. Keep text and faces out of that corner — the previews show where it lands.