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
AI answer card
Quick answer
- Best size
- Check the final exported image file before upload, then judge size by the destination surface rather than one universal image dimension
- Best ratio
- Depends on the use case: 16:9 for standard YouTube thumbnails, 9:16 for vertical social, 1:1 or 4:5 for many feed images, wide ratios for banners, and about 1.91:1 for Open Graph cards
- Use when
- Use this workflow when you have a finished JPG, PNG, WebP, AVIF, or GIF and need to confirm width, height, aspect ratio, file size, format, and the right ImageSizeKit route before publishing.
- Avoid
- Avoid checking only the design canvas, template preset, screenshot, or CMS preview. The downloaded upload file can have different dimensions, compression, or format.
- Check with
- Image Size Checker
- Last checked
- August 9, 2026
- Source boundary
- ImageSizeKit reads image dimensions locally in the browser for pre-upload checks. Destination platforms can still apply their own crop, compression, cache, and upload rules.
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 decision path
Use this gate before publishing when you have a finished image file but are not sure which checker or guide should judge it. The first decision is the destination, not just the pixel count.
| Current state | Best next step | Why | Route |
|---|---|---|---|
| I have an unknown exported image file | Start with the general Image Size Checker. | Read width, height, ratio, format, file size, and the nearest ImageSizeKit workflow before choosing a platform guide. | Run image check |
| The file is a YouTube thumbnail candidate | Use the YouTube thumbnail checker. | A YouTube thumbnail needs the 16:9 ratio, platform-specific dimensions, format, file-size, and upload readiness checks together. | Check YouTube thumbnail |
| The file is for social, creator, or ecommerce publishing | Use the Social Media Image Checker. | The same image may be a square post, vertical cover, profile image, product photo, marketplace listing, or banner candidate. | Route social image |
| The file is for a website preview or link card | Use the Open Graph Preview Checker. | Website previews need image dimensions plus page metadata checks, so separate raw file problems from og:image and cache problems. | Check OG preview |
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.
Canonical image dimension pre-upload result action map
Use this short map after the first file check. It turns the result into one next action: read final file facts, choose the publishing surface, route thumbnail-like images, separate banner and Open Graph risks, or re-export a cleaner source file.
Unknown final file
Run image checker
Run the canonical Image Size Checker first and keep width, height, ratio, file size, format, and nearest route.
Destination is unclear
Choose route
Choose the publishing surface before resizing: thumbnail, social post, banner, product image, or Open Graph preview.
Thumbnail-like image
Check thumbnail
Route 16:9 files through YouTube thumbnail checks before approving text, format, file size, or reuse.
Wide or website-preview image
Check banner crop
Split banner crop checks from Open Graph preview checks so a wide file is not forced into the wrong workflow.
Too small or soft export
Calculate replacement
Calculate a clean replacement canvas and re-export from the source file instead of resizing a proxy image.
Image upload repair priority matrix
Use this matrix when an exported image fails a check or you are not sure which problem to fix first. Confirm the file is the true upload asset, route it by publishing surface, then repair thumbnail, banner, Open Graph, product, or softness issues in that order.
| Priority | Symptom | Fix first | Why it matters | Next route |
|---|---|---|---|---|
| 1 | You only have a screenshot, preview download, or CMS thumbnail | Find the original exported file before judging dimensions. | Proxy files can report real pixels while still being the wrong upload asset, so resizing them usually makes quality worse. | Check final file |
| 2 | The final destination is still unclear | Route the file by publishing surface before resizing. | A 16:9 file, a wide banner, and a 1.91:1 card can look similar in a folder but need different checks before upload. | Route image surface |
| 3 | The file is 16:9 and thumbnail-like | Decide whether it is a YouTube thumbnail, video card, marketplace show image, or Open Graph preview. | Thumbnail-like images often fail because they are reused across YouTube, social, marketplace, and website contexts without a separate export. | Check thumbnail route |
| 4 | The file is wide and header-like | Check banner crop and safe areas before moving text or logos. | Wide images can pass a dimension check while hiding important content on mobile, profile, or cover surfaces. | Check banner crop |
| 5 | The file is a website share image | Separate file dimensions from Open Graph metadata and cache behavior. | A correct 1200 x 630 file can still show a blank, stale, or wrong URL preview after publishing. | Check OG preview |
| 6 | The file is a product or marketplace image | Route it to product-image guidance instead of generic social image guidance. | Product detail, zoom quality, square crops, and marketplace cards are different publishing jobs from social posts. | Check product image |
| 7 | The destination is clear but the file is too small or soft | Calculate a clean replacement canvas and re-export from the source. | After routing is clear, remaining softness is usually a source-size, compression, or export settings problem. | Calculate replacement |
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.
Image dimension pre-upload acceptance record
Use this record when an image is ready to upload, schedule, or hand off. It keeps the final file identity, measured dimensions, publishing surface, platform route, re-export decision, and privacy boundary together so the dimension check becomes a usable approval package.
| Acceptance package | Evidence to keep | Reject when | Next route |
|---|---|---|---|
| Final upload file identity | The exact JPG, PNG, WebP, AVIF, or GIF that will be uploaded has been checked, not a design canvas or preview. | The file is a screenshot, CMS thumbnail, chat preview, social download, or compressed copy of the real source export. | Check final file |
| Measured file facts | Width, height, aspect ratio, file size, format, orientation, and nearest ImageSizeKit route are kept with the task. | Only the intended design size is known, or the result is copied without file size, format, and route context. | Keep checker result |
| Publishing surface decision | The destination is named before upload: YouTube thumbnail, social post, banner, product image, website preview, or another surface. | The file is resized before anyone chooses the actual publishing surface. | Choose next route |
| Platform route acceptance | The measured file is sent to the smallest matching checker or guide instead of staying in a generic dimensions workflow. | A 16:9, square, vertical, wide, or 1.91:1 file is approved without platform-specific crop and upload checks. | Route image surface |
| Re-export decision | The next action is explicit: approve, crop, re-export larger, change format, compress once, or return to source artwork. | The same file is edited repeatedly without identifying the first failed gate. | Calculate replacement |
| Privacy and handoff boundary | The team knows local dimension checks happen in the browser, and the final result can be shared without attaching the image unnecessarily. | A sensitive file is uploaded or forwarded just to prove width, height, ratio, format, or file size. | Review privacy boundary |
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: August 9, 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.