Unable to insert AVIF images into CKEditor in Drupal 11 using IMCE

Problem/Motivation

In Drupal 11, when using the IMCE module, I am able to successfully upload .avif images. However, after uploading, I cannot insert the AVIF image into CKEditor 5 content.

Other image formats (e.g., JPG, PNG, WEBP) work as expected. The issue only occurs with .avif images.

I have disabled the “Enable image uploads” option in CKEditor 5, so image insertion depends on IMCE. This makes the issue more noticeable, as IMCE upload works fine, but insertion into the editor fails.

Possibly IMCE needs to declare .avif as a supported extension for insertion.

Steps to reproduce

1. Install Drupal 11 with CKEditor 5 enabled.
2. Install and enable IMCE module.
3. In CKEditor 5 configuration, disable the “Enable image uploads” option.
4. Upload an .avif image using IMCE.
5. Attempt to insert the .avif image into CKEditor 5 content.

Expected result

The uploaded AVIF image should be insertable into CKEditor 5, just like JPG or PNG.

Actual result

Upload works fine, but the AVIF image cannot be inserted into CKEditor 5.