YouTube thumbnail preview tool
A preview is not an upload check.
Use a mockup to inspect how an image and title look together. Before you publish, separately check the file against the upload route you will actually use. YouTube's documented size limits differ by device, and a preview cannot tell you whether your account or upload will be accepted.
Choose the upload route before exporting
| What you are uploading | Route to check | Official file guidance |
|---|---|---|
| Regular video thumbnail | Desktop YouTube Studio | JPG or PNG; 16:9 recommended; desktop limit listed as 50 MB. |
| Regular video thumbnail | YouTube mobile app | Mobile video-thumbnail limit listed as 2 MB. |
| Podcast thumbnail from mobile | YouTube mobile app | Podcast limit listed as 10 MB; do not apply the video limit to this case. |
| Short thumbnail | YouTube Studio on a computer | 9:16 is recommended for an uploaded Short thumbnail. This is not the regular-video 16:9 check. |
YouTube's Help Center also says a vertical video's 16:9 custom thumbnail is replaced by an auto-generated 4:5 thumbnail on Home, Explore, and Subscriptions; the custom image remains on watch surfaces and non-mobile platforms. That display rule is separate from whether a file opens in a preview.
A practical preview-to-upload preflight
- Pick the destination first. Decide whether this is a regular video, a Short, or a podcast image, and whether you will upload from desktop or mobile.
- Use a preview for visible questions. Check the crop, focal point, title beside the image, and whether the main visual still reads in a smaller layout. Open the local thumbnail tester or read the thumbnail checker routine.
- Check the exported file separately. Confirm its actual pixel dimensions, file type, and file size after export. A mockup can render an image even when the publishing route has a stricter limit.
- Upload through the selected route. If YouTube rejects the file, adjust the export for that route; do not infer upload eligibility from a successful local preview.
- Verify the published display. After saving, check the video on the surfaces where YouTube says the thumbnail is shown. A preview tool cannot guarantee every device will render an identical crop.
What a YouTube thumbnail preview tool can establish
A preview establishes only what its mockup displays. Thumbnail Inspector places one selected image and a working title in sample layouts and reads local image facts; it does not contact YouTube, submit the file, inspect account eligibility, or predict the final platform result. See the thumbnail preview review guide for the visual side of that check.
For API uploads, Google's YouTube Data API documentation lists its own media constraints. Treat those as API-method requirements, not as a substitute for checking the route and device described in YouTube Help.
YouTube thumbnail preview tool FAQ
Does a successful preview mean YouTube will accept the image?
No. The preview is a local mockup. Check the image against the upload route's current requirements and verify it in YouTube Studio after upload.
Why can a file work on desktop but fail on my phone?
YouTube documents different file-size limits by upload device. Check the current Help Center limit for the route you will use.
Can a regular-video preview confirm a Short thumbnail?
No. YouTube recommends a different aspect ratio for Shorts, and the documented display behavior differs from a regular video.
Does the YouTube Data API have the same rules as every upload screen?
The API reference describes the constraints of its thumbnail-setting method. Use it for API uploads; use YouTube Help for Studio and mobile workflows.
Sources and scope
- YouTube Help: Add custom thumbnails — file formats, size guidance, upload routes, and display notes.
- YouTube Data API: thumbnails.set — constraints for the API upload method.
- YouTube Creators: How to Add Custom Thumbnails to Your YouTube Videos — official upload walkthrough.
This guide turns those route-specific rules into a preflight sequence. Requirements can change; check the linked official documentation when exporting.