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Private local image check

YouTube Thumbnail Size Checker & Preview

Check dimensions, aspect ratio, format, and file size before upload. Preview how your image scales in several common YouTube-style placements.

Upload validator

Choose a thumbnail image

Image stays on your device

YouTube thumbnail dimensions and ratio

For a standard video, a 16:9 image avoids unexpected cropping in most video placements. For Shorts, use a vertical 9:16 image. Higher-resolution files leave more detail when the interface displays the thumbnail on larger screens, but the final appearance still depends on YouTube’s processing and layout.

What the validator checks

  • Pixel width and height.
  • Measured aspect ratio compared with the selected video type.
  • JPG, PNG, or WebP format.
  • File size for your own upload check.
  • Whether the shortest image dimension reaches 640 pixels.

TubeRank does not upload the image and does not predict click-through rate. File-size allowances can vary by upload surface, device, account, and future platform changes, so confirm the current limit shown in YouTube Studio if the upload is rejected.

Design checks before you publish

  1. View the thumbnail small enough that details disappear; the main subject should still be obvious.
  2. Keep essential text and faces away from the lower-right duration area.
  3. Use accurate imagery and wording that match the video.
  4. Compare two real designs with YouTube’s native Test & Compare feature when it is available to your channel.

Frequently asked questions

Does this tool upload my thumbnail?

No. The browser reads the selected file locally to calculate dimensions and render previews.

Does a passing result guarantee the same crop everywhere?

No. YouTube can change its layouts, overlays, and crops. The previews are practical approximations.

Can TubeRank predict thumbnail CTR?

No. Click-through rate depends on the audience, topic, impression source, title, competition, and placement. Use YouTube Analytics and native experiments for measured results.

Updated August 2026

Timestamp & Chapter GeneratorCreate share links and validate YouTube chapter formatting. Thumbnail Size CheckerValidate an upload locally and preview common placements.

How to evaluate a thumbnail preview

The previewer places the uploaded image into representative YouTube-style layouts so you can inspect legibility, cropping, contrast, and visual hierarchy before publishing. It does not upload the image to YouTube or predict click-through rate.

A focused preview checklist

  1. Use the final thumbnail file and add the exact intended video title.
  2. Inspect both the smaller sidebar view and the larger search or homepage view.
  3. Check whether the main subject remains recognizable at the smallest size.
  4. Remove tiny text, crowded details, or imagery that creates a false expectation.

Example interpretation

A thumbnail may look clear at full size but lose its subject when reduced. If a face, product, or result is important, it should remain visually distinct in the sidebar preview. Text should complement the title instead of repeating it word for word. A clean preview only confirms presentation; it does not prove that viewers will click.

Limits and file handling

Real YouTube layouts vary by device, account, experiment, theme, and language. Cropping and overlays may change. Use an image you own or have permission to test, and avoid misleading imagery. YouTube’s thumbnail documentation explains thumbnail resources. Use the Thumbnail Downloader only for images you are permitted to save.

Preview workflow reviewed by TubeRank on August 12, 2026. The mockups are representative and cannot reproduce every live YouTube interface.