The design canvas was correct, but the downloaded file changed size.
Check the final downloaded file, then re-export from the original canvas if the dimensions changed.
Pre-upload workflow
How to check image dimensions before uploading
Most upload problems begin before the upload button. Check the final JPG, PNG, WebP, AVIF, or GIF file first: width, height, aspect ratio, file size, format, and the ImageSizeKit route that matches the publishing surface.
Local file factsAspect ratioFormat checkPublishing route
Quick answer
Check the final exported file, not just the design canvas. A Canva, Figma, Photoshop, CMS, or mobile editor preset can say one size while the downloaded file has a different pixel width, height, ratio, or compression level.
After measuring the file, route it by purpose. A 16:9 image may be a YouTube thumbnail. A 1.91:1 image may be an Open Graph preview. A wide header may need a banner safe-area check before upload.
Pre-upload image dimension workflow
- Export the final image file from the design tool, CMS, editor, or phone app.
- Check the actual width, height, aspect ratio, file size, and format.
- Decide the publishing surface: thumbnail, social post, banner, product image, or Open Graph preview.
- Open the matching ImageSizeKit checker or guide before uploading.
- Re-export a separate file when one design needs another platform crop.
What to check in the exported file
| Signal | Why it matters |
|---|---|
| Width and height | Confirms the real pixel dimensions of the exported file. |
| Aspect ratio | Shows whether the file is 16:9, 9:16, 1:1, 1.91:1, 4:1, or another shape. |
| File size | Helps catch oversized uploads or files that were compressed too aggressively. |
| Format | Helps choose JPG, PNG, WebP, AVIF, or GIF based on the artwork and upload surface. |
| Next route | Turns the raw file facts into the closest ImageSizeKit guide or checker. |
Route the checked image by publishing surface
The checker gives file facts. The next page should match the real publishing surface, not the name of the file.
YouTube standard video thumbnail
YouTube thumbnail size
Usually a 16:9 image. A 1280 x 720 export is a common HD target.
Instagram, LinkedIn, Facebook, or mixed social image
Social media image checker
The same file may be square, vertical, wide, or a platform-specific cover.
Website link preview or og:image
Open Graph preview checker
A practical default is often 1200 x 630, close to a 1.91:1 ratio.
Wide header, banner, channel art, or cover image
Banner size checker
The file can be wide enough but still crop important text on mobile.
Common mistakes this prevents
The file is 16:9, but text looks soft after upload.
Check file size and format, then review the JPG vs PNG guide before exporting again.
The image is large enough, but a banner crop cuts off text.
Open the banner checker and platform safe-area guide before moving text or logos.
A screenshot is being used as the upload file.
Find the source export when possible because screenshots and preview downloads are often smaller than the production image.
Privacy boundary
ImageSizeKit checker tools read the selected file in your browser for basic dimension checks. They do not upload or store the selected image just to report width, height, ratio, format, and file size.
Last checked: July 30, 2026
FAQ
Why should I check image dimensions before upload?
The final exported image can differ from the design canvas. Checking dimensions before upload catches wrong width, height, aspect ratio, format, and file size before a platform crops or compresses the image.
Should I use an image size checker or a platform guide first?
Use an image size checker first when you only have a file. Use a platform guide first when you already know the destination, such as YouTube thumbnail, LinkedIn banner, or Open Graph image.
Does ImageSizeKit upload my selected image?
No. ImageSizeKit checker tools read selected image files locally in the browser for basic dimension checks.