YouTube thumbnail tester
Preview your thumbnail at the size viewers actually see it: home grid, search, suggested sidebar and mobile feed, light and dark, with the duration badge on top. Check it against YouTube's specs and place it among competitors.
Home grid (desktop)
Search results (desktop)
Suggested sidebar
Mobile feed
Sizes are approximations of YouTube's layouts at common screen widths, measured from the site and apps; YouTube changes them often.
4 steps, no signup
- 01
Upload your thumbnail
Choose or drop a JPG or PNG. It is checked against YouTube's current thumbnail requirements straight away.
- 02
Add a title and channel name
Type the title as it will appear. Long titles are cut to two lines, just as YouTube does.
- 03
Compare the layouts
See the thumbnail at real size in the home grid, search results, suggested sidebar and mobile feed, in light and dark mode, with the duration badge on top.
- 04
Add competitors
Upload thumbnails you will be shown next to. Yours is placed among them in random order, so you can judge whether it stands out.
What this YouTube thumbnail tester does
You design a thumbnail at full screen, but almost nobody sees it that way. On the home page it is a card a few hundred pixels wide; in the suggested sidebar it is smaller than a matchbox; and the video length sits on top of its bottom-right corner. This YouTube thumbnail tester puts your image into mock YouTube layouts at those real sizes, with your title and channel name, so you can see what a viewer sees before you publish.
Most thumbnail preview sites show one large mock-up, often in light mode only. The checks that matter are different: does the text still read at 168 pixels wide, does the badge hide anything, does it survive dark mode, and does it stand out next to the other videos in your topic? That is what this page is built around.
YouTube thumbnail requirements
Taken from YouTube's help article Add video thumbnails, checked on the date at the bottom of this page:
| Requirement | Videos |
|---|---|
| Recommended resolution | 3840×2160 |
| Minimum width | 640 px |
| Aspect ratio | 16:9 |
| Formats | Image formats such as JPG or PNG |
| File size | 50 MB on desktop; 2 MB from the mobile app |
Many guides still quote 1280×720 and a 2 MB limit. Those were the rules for years, and a 1280×720 file under 2 MB still uploads everywhere, so it remains a safe choice. YouTube's current recommendation is higher, which matters most on large screens such as TVs. Shorts thumbnails follow different rules (9:16, minimum height 640 px) and are not covered by this tool.
Uploading a custom thumbnail also requires a verified account, and thumbnails must follow YouTube's Community Guidelines.
The duration badge
Every long-form thumbnail carries the video length in a small dark box in the bottom-right corner. Watch progress bars also appear along the bottom edge for videos someone has partly watched. Anything important placed there, such as the last word of your text or a logo, can be covered. The preview draws the badge where YouTube puts it, using the duration you type.
Read it at the smallest size
The suggested sidebar is the toughest test. At about 168×94 pixels, thin fonts, small faces and more than three or four words turn into noise. A practical routine:
- Check the sidebar version first. If the idea reads there, it will read everywhere.
- Don't repeat the title. The title appears next to the thumbnail; the image can add to it instead of duplicating it.
- Switch to dark mode. Dark edges disappear into a dark interface; a thin border or brighter background can help.
- Watch the title length. YouTube cuts titles to two lines in most layouts. The preview clamps them the same way.
Compare against competitors
A thumbnail is never seen alone. Download a few thumbnails from videos in your topic with our YouTube thumbnail downloader, add them under Competitor thumbnails, and yours is placed among them. Press Shuffle order a few times and look away between shuffles: if you cannot find your own thumbnail in a second, neither can a viewer.
A preview tells you about legibility and contrast. It cannot tell you click-through rate. To measure that, publish and compare, or use YouTube Studio's own thumbnail testing feature where your channel has it.
Light mode, dark mode and TV
YouTube can follow the device's light or dark setting, so some of your viewers will see dark mode, and the same thumbnail can look very different on a white page and a near-black one. Dark thumbnails lose their edges on a dark interface and can look like an empty slot; very bright, white-background thumbnails can glare in dark mode. Toggle the theme above and look at the whole grid rather than your thumbnail alone. If yours melts into the background in one mode, a brighter subject, a coloured background or a subtle outline usually fixes it.
Thumbnails also appear on TVs and in the YouTube app on tablets, where they are larger and any softness shows. That is a likely reason for YouTube's 3840×2160 recommendation (YouTube doesn't say): a 640 px wide image meets the minimum but will look blurry on a living-room screen.
Common thumbnail problems this catches
- Text hidden by the badge. The last word of a right-aligned headline sits under the duration.
- Unreadable small text. Anything below roughly a tenth of the image height disappears in the sidebar.
- Wrong shape. A 4:3 or square export gets bars or a crop; the spec check flags it.
- Too similar to competitors. The same colour and layout as every other video in the topic.
- Mobile-only file size problems. A file over 2 MB uploads on desktop but fails from the app.
Privacy
Your thumbnail and competitor images are displayed with object URLs in your browser. Nothing is uploaded.
Last checked and updated: . Everything on this page runs in your browser; nothing you enter is sent anywhere.