Image Optimization Troubleshooting

Learn how to identify and resolve common issues when using Image Optimization on Medianova CDN.

This page describes the most common failure scenarios, their causes, and the actions required to resolve them.

Resolve 415 Unsupported Media Type errors

A 415 – Unsupported Media Type error occurs when Image Optimization cannot process the requested image.

When this happens

Image Optimization returns 415 in the following cases:

• The image file exceeds supported size or dimension limits

• The image format is not supported

• The image file extension and Content-Type (MIME type) do not match

Check file size and dimensions

Image Optimization supports images up to a defined size and resolution.

Limits

• Maximum file size: 25 MB

• Maximum dimensions: 3000 × 3000 pixels

If the image exceeds these limits, the CDN returns 415.

How to fix

• Reduce the image file size

• Resize the image to stay within supported dimensions

• Upload a smaller version of the image to the origin

Check supported image formats

Image Optimization supports the following source formats:

• JPEG

• PNG

Requests for other image formats return 415.

How to fix

• Convert the image to JPEG or PNG before uploading

• Update image URLs to reference a supported format

Check Content-Type consistency

A 415 error may occur when the image file extension does not match the Content-Type returned by the origin.

Example

• File extension: .png

• Returned Content-Type: image/x-ms-bmp

Although the file extension is supported, the actual media type is not compatible with Image Optimization.

How to fix

Recommended

Configure the origin or storage to return the correct MIME type.

Content-Type: image/png

This may require re-uploading the file or updating object metadata in your storage system.

Temporary workaround

If the origin cannot be modified immediately, apply a Page Rule on the CDN Resource:

• Match path: *.png

• Add response header:

  Content-Type: image/png

Header overrides do not change the actual file content. Ensure that the image format matches its file extension.

Resolve unsupported transformation requests

Some transformation requests may fail even when the source image is valid.

Check transformation parameters

Invalid or unsupported transformation parameters may cause the request to fail.

How to fix

• Verify that all transformation parameters follow the documented syntax

• Ensure numeric parameters use valid values

• Remove unsupported or conflicting parameters

Refer to the Image Optimization documentation for supported modules and parameters.

Resolve cache-related inconsistencies

Each transformed image URL is cached as a separate object.

If an image was previously cached with incorrect content or headers, unexpected behavior may occur.

Clear cached variants

How to fix

• Purge the specific transformed image URL

• Re-request the image after correcting the origin configuration

Purging the original image URL does not remove transformed variants. Each transformed URL must be purged individually.

Verify browser compatibility for WebP

WebP delivery depends on browser support.

If a browser does not support WebP, the CDN serves a fallback format.

This behavior does not cause a 415 error.

How to verify

• Test the image URL in different browsers

• Inspect the Content-Type response header

When to contact Medianova Support

Contact Medianova Support if:

• The image meets all size, format, and MIME requirements

• The issue persists after cache purge

• The error occurs intermittently across regions

Include the following information when contacting Support:

• Image URL

• CDN Resource name

• Approximate time of the request

• Observed HTTP status code

Summary

Use this checklist when troubleshooting Image Optimization issues:

• Verify image size and dimensions

• Confirm supported image format

• Ensure correct Content-Type from the origin

• Validate transformation parameters

• Purge cached transformed URLs when needed

Following these steps resolves most Image Optimization errors without additional support.