Free tool · no account needed
Check your thumbnail before publishing
Inspect the actual dimensions and size of your download, then view a small crop to spot unreadable text or hidden subjects. This checks the file you choose; it does not generate, resize, or compress an image.
Your selected image stays in this browser. This tool does not send it to SocialThumbPro or an AI service.
JPG, PNG, or WebP · up to 50 MB and 40 megapixels
What this check can tell you
Dimensions and file size are measurable. Readability, accurate claims, rights to the image, and whether it represents your video still need your judgement. A green check does not certify platform approval.
YouTube recommendations checked 4 October 2026. Read the current official upload requirements.