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Uploading .CR3 files to AEM Assets fails due to MIME type configuration

Last update: Mon Apr 06 2026 00:00:00 GMT+0000 (Coordinated Universal Time)

Uploading Canon RAW (.CR3) files to Adobe Experience Manager (AEM) Assets fails with a restriction or invalid format error even after adding expected MIME types to upload restrictions. This happens because the upload client performs a case-sensitive MIME type check based on what the browser sends, and the backend requires a correctly formatted global MIME mapping. To fix this, add all required case-sensitive CR3 MIME types to upload restrictions and configure the global MIME mapping using whitespace instead of an equals sign.

Description description

Environment

  • Product: AEM as a Cloud Service - Assets

  • Constraints:

    • Observed on Chrome running on Windows
    • Configuration is environment-specific
    • Changes don’t automatically propagate across environments

Issue / Symptoms

  • Uploading .CR3 files results in a restriction or invalid format error
  • The browser reports the file type as image/CR3 (uppercase subtype)
  • The upload client performs a case-sensitive MIME type match
  • Backend logs show a null or undetectable MIME type during initiateUpload

Resolution resolution

To fix the issue, follow these steps:

  1. Log in to each affected AEM author environment such as development or production.

  2. Go to Tools > Assets > Assets Configurations > Upload Restrictions.

  3. Add the following MIME types to the allowed list:

    • image/x-canon-cr3
    • image/cr3
    • image/CR3

  4. Save the changes.

  5. Update the global MIME mapping in the OSGi configuration for org.apache.sling.commons.mime.internal.MimeTypeServiceImpl using whitespace instead of an equals sign:

    image/x-canon-cr3 cr3

  6. Deploy the configuration through your code repository and Cloud Manager pipeline.

  7. Repeat these steps in every environment where .CR3 uploads are required.

  8. Verify that .CR3 files upload successfully without restriction errors.

Notes

  • Upload restrictions rely on the MIME type sent by the browser, which is case-sensitive and platform-dependent.
  • Global MIME mapping affects backend processing only.
  • UI-based configuration changes can be overwritten during redeployments.
  • Each environment requires separate configuration.
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