Maintained by Image Reshaper · Updated
Fix Image Upload Errors: File Size, Dimensions and Format
Check byte limits, pixel dimensions and actual image format before retrying an upload. Includes invalid-file examples.
Check bytes, dimensions and real format
A file can satisfy a size limit and still fail a dimension or format rule. Read the destination’s requirements and check all three before retrying. Changing .png to .jpg does not convert the image.
Image Reshaper accepts JPG, PNG and WebP in the standard tools, up to 20 MB per file, 8192 pixels per side and 25 million pixels. HEIC has its own converter. SVG, GIF, PDF and arbitrary renamed files are not accepted by the standard uploader.
Match the fix to the error
Our automated fixture check renames plain text to .jpg and sets its MIME type to image/jpeg. It is rejected because the bytes do not identify a JPG. A 21 MiB input is also rejected before decoding. These are validation examples, not a claim that every malicious file can be detected.
If a valid image cannot be decoded, export a new copy from a trusted image editor. If your browser cannot encode WebP, choose JPG or PNG. For a portal-specific error after download, check its own format and minimum-dimension rules.
- For too many bytes, use target-size compression and inspect its result.
- For incorrect width or height, use Image Resizer with the required fit or crop mode.
- For the wrong format, use Image Converter and download the new file.
- For an unreadable file, try a fresh export rather than repeatedly renaming it.
Try our measured examples
Created and tested on 2026-10-06 in Chrome 154.0.8037.98. These images were generated by this project. Results vary with source content and browser encoder; no camera photograph was used.
Real validation checks rejected text renamed to JPG and a 21 MiB file. The same run verified that an impossible one-byte output target reports failure. These checks are reproduced by scripts/measure-images.cjs in the project.
Method: deterministic Canvas-generated 1200 × 800 sources, the production renderImage/compressToMaxBytes functions, quality 80 for format comparisons, and an automatic bounded search for byte targets. Resize examples export PNG. No measurements of network speed or field Core Web Vitals are implied.