Every video platform covers part of your thumbnail with its own interface. If you don't plan for it, the platform will quietly cover the most important part of your design. Here is a practical checklist for both horizontal thumbnails and vertical 9:16 covers, using free browser tools from ThumbProof.
Horizontal thumbnails (16:9)
1. Start at the right size. Design at 1280×720 and keep the file under 2 MB. If your export is too large, ThumbProof's Thumbnail Resizer can resize and crop to 1280×720, and the homepage can compress oversized images locally to a JPEG under 1.9 MB.
2. Keep the bottom-right clear. This is where the duration badge sits. Text, a face or a logo here gets partly covered. The Safe Zone Checker shows the badge area on a large canvas and warns you when the bottom-right corner is too busy.
3. Watch the bottom edge. For viewers who have partly watched a video, a progress bar runs along the bottom. Don't put essential text right at the edge.
4. Account for hover icons. On desktop, hovering can show small icons over the thumbnail. The checker overlays those zones too.
5. Check it small. Look at the thumbnail at 246×138, 168×94 and 120×68. If the main subject isn't recognizable at sidebar size, simplify it with fewer words, a bigger face, or stronger contrast.
6. Check contrast in grayscale. A thumbnail that relies on color alone tends to blend into a busy feed. ThumbProof's grayscale and blur ("squint") overlays make this easy to judge.
Vertical covers (9:16)
Vertical videos in Shorts and Reels formats have a different set of covered areas. The title and channel information sit near the bottom, and action buttons run up the right side. Profile grids may also crop your cover to 4:5 or 1:1.
7. Keep the center clear and readable. ThumbProof's Shorts & Reels Cover Preview places your 9:16 cover in a vertical shelf with the title and side-button overlay zones visible.
8. Test the crops. The same tool shows the 4:5 and 1:1 profile-grid crops, so you can confirm the subject survives when the top and bottom are cut off.
Titles count too
9. Front-load the title. Titles get cut off at different widths in different layouts. ThumbProof's title truncation meter estimates where an ellipsis may land on desktop, mobile, search and sidebar, so the key words stay visible.
Final pass
10. See it in the feed. Drop the finished thumbnail into the Feed Preview and look at it next to other thumbnails in a desktop grid, mobile feed, search results, sidebar and TV view. Problems that are invisible on a blank canvas often stand out immediately among the competition.
All of these tools are free, need no account, and process your images locally in the browser, so nothing is uploaded. They are also available in 11 languages. The previews are approximations of real interfaces, not exact copies, but they are close enough to catch the mistakes that matter: covered text, cut-off titles, and designs that disappear at small sizes.
Save this checklist and run through it before every upload. It takes a couple of minutes, and the platform's interface won't cover your thumbnail's best part.
Key features of ThumbProof
Preview and inspection
- Feed Preview for 1–4 thumbnails with per-thumbnail titles (drag, click, or paste)
- Simulated desktop 3-column home feed, mobile feed, search results, sidebar (168×94) and TV view
- All Sizes view: 1280×720, 360×202, 320×180, 246×138, 168×94, 120×68
- Overlays for the duration badge, hover icons and progress-bar safe zones; squint (blur) and grayscale checks
- Title truncation meter across feed layouts
Testing and file tools
- Visual audit score from 0 to 100, plus local compression to a JPEG under 1.9 MB for files over 2 MB
- A/B Tester for 2–4 versions with a 5-round blind test (pick rate and average reaction time) and a side-by-side PNG export
- Safe Zone Checker, Shorts & Reels Cover Preview (9:16, 4:5, 1:1) and Thumbnail Resizer
- 100% in-browser, images never uploaded, no sign-up, free (ad-supported), 11 interface languages
Use cases
- Check a new thumbnail's legibility at small feed and sidebar sizes before publishing
- Choose between 2–4 thumbnail concepts with a blind first-glance test
- Make sure text, faces or logos are not hidden under the duration badge or progress bar
- Find out whether a title will be truncated on desktop, mobile, search or sidebar
- Preview vertical 9:16 covers for Shorts/Reels-format videos and their profile-grid crops
- Show a client or team a side-by-side comparison image, and test privately since nothing leaves the device
Step-by-step: your first preview
1. Open visual audit score from 0 to 100 for thumbnail resolution, contrast and sharpness (https://thumbnailpreview.app/).
2. Drag, click or paste one to four thumbnails and give each a title.
3. Switch between desktop, mobile, search, sidebar, TV and All Sizes views; try dark and light mode.
4. Turn on the safe-zone overlays, the squint test and grayscale.
5. Read the visual audit score and the title truncation meter, then fix what they flag.
6. Optionally open the A/B Tester and run five blind rounds before you publish.
FAQ
Are my images uploaded or stored?
No. Everything runs in your browser, and images are never uploaded to a server.
Do I need an account?
No. The tool is free and needs no registration or login. Ads support the site.
Are the previews identical to real platforms?
No. They are simulated approximations meant as a realistic visual reference.
Will it raise my views or CTR?
No. ThumbProof doesn't influence algorithms, rankings or click-through rates. It is an inspection and layout tool.
Is it affiliated with a video platform?
No. ThumbProof is independent. You must be 16 or older to use it.
Join Qfeast to read the entire story!
Sign In. It is absolutely free!