KiiMix YouTube Thumbnail Size & Free Online Cropper
Make a 3840 × 2160 YouTube thumbnail with a free online cropper. Crop to 16:9 in your browser, without uploading images. Export JPEG.
How to use
- 1Select or drop up to 12 images, no larger than 20 MiB each.
- 2Choose a preset or free crop, adjust the crop box, and set the JPEG quality.
- 3Start processing and download each result. Transparent backgrounds become white.
Specifications & output
Crop a thumbnail for a regular YouTube video. The preset exports a 3840 × 2160 JPEG at 16:9. Adjust the crop box to keep your subject and text in view.
| KiiMix default output | 3840 × 2160 px |
|---|---|
| Video thumbnail guidance | 3840 × 2160 px; 16:9 |
| Minimum width | 640 px |
| Accepted upload formats | JPG / PNG |
| Video thumbnail upload limit | Mobile: 2 MB; desktop: 50 MB |
Platform documentation & further reading:
- YouTube Help — Custom thumbnails Source checked:
Keep the thumbnail readable
Choose one main subject and give any text enough contrast against the background. Check the image at a small size: faces, products and the title should still be easy to make out.
Check upload size after export
Check the exported file size in the results list against the upload limit for your device. If it is too large, lower JPEG quality and process it again. Matching the pixel dimensions alone does not guarantee the file will be small enough.
Frequently asked questions
What size should a video thumbnail use?
YouTube Help recommends 3840 × 2160 for video thumbnails, which is the size this preset exports. Use a large enough source image: enlarging a small image will not add detail.
Can I use this for a Short?
This preset is for 16:9 regular-video thumbnails. YouTube separately recommends 9:16 for Shorts; use an appropriate vertical crop instead.
Why does a wide thumbnail look cropped elsewhere?
YouTube can display thumbnails differently for vertical videos. Check the upload preview and the places where the thumbnail will appear; the full image may not be shown everywhere.
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