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Verify if your thumbnail matches YouTube's recommended resolutions, file sizes, and format rules.
Getting ready to publish a new video? Don't let an upload rejection slow your publish schedules down. Our Free online Thumbnail Size Checker validates your design files against YouTube's official limits for resolution, aspect ratio, file format, and file size.
To keep the platform looking clean and loading fast, YouTube enforces specific constraints on custom video covers. If you ignore these rules, your file will either be rejected by the creator dashboard, or scaled automatically, resulting in black bars, pixelation, or cropped text. Meeting the standard rules is crucial for high-quality visuals:
Instead of manually checking file properties on your desktop or guessing dimensions, you can drag your final image into the Thumbnail Size Checker. In milliseconds, the tool extracts the image's height, width, size in bytes, and format type, showing green checkmarks for all passing items. This prevents workflow disruptions when saving files from design suites like Figma, Photoshop, or Canva. Before uploading, you can also test readability under actual feed conditions using our YouTube Thumbnail Preview simulator.
For official support guides, read Google's Custom Thumbnail Requirements Page and verify mobile app layout setups via the YouTube Creator Hub.
YouTube officially recommends a resolution of 1280 x 720 pixels, with a minimum width of 640 pixels. The image must be in a 16:9 aspect ratio (widescreen). Uploading files with these dimensions ensures your cover renders clearly on high-definition screens and matches the standard desktop and mobile player aspect ratios without black margins.
The maximum file size allowed by YouTube for custom video thumbnails is 2 Megabytes (2MB). If your design file exceeds 2MB, YouTube's video manager will reject the upload, throwing a file size error. To prevent this, you can compress your JPG, WebP, or PNG file using our Image Compressor tool before uploading.
YouTube accepts four main image formats for custom thumbnail uploads: JPEG (JPG), PNG, GIF (non-animated), and BMP. Modern formats like WebP are becoming supported on newer developer channels, but for standard uploads, saving your files as JPEG or PNG remains the safest choice to prevent upload rejects.
Our Thumbnail Size Checker handles this automatically. When you upload your cover image, the tool reads the image's physical width and height to calculate the exact ratio. A standard 1280x720px graphic yields a perfect 16:9 (1.777) aspect ratio, passing the check. If your ratio is incorrect (e.g. 4:3 or 1:1), you will see a warning.
Upload rejections are almost always caused by three issues: the file size is over 2MB, the file format is unsupported (such as TIFF or raw HEIC formats from iPhones), or your Google account has not been verified yet. Custom thumbnail uploads require a verified phone number connected to your YouTube channel account.
Yes, 1920x1080 (Full HD) images work perfectly because they share the exact same 16:9 aspect ratio as 1280x720. They will render beautifully on large displays. However, high-resolution graphics often exceed the 2MB file limit, so ensure you compress the file size before attempting to upload.
Yes, our checker is completely free and operates client-side inside your browser. Your images are never sent to external servers or cloud processors. The image parameters are read locally using browser File Reader APIs, keeping your pre-release content and layout designs 100% confidential.
Instant, browser-local utilities to streamline your digital workflows.