HEIC images no longer are converted automatically to JPEG

[annezazu]

Context and steps to reproduce

As of WordPress 6.7, Core should automatically create a JPEG version of uploaded HEIC images if the server has a version of Imagick that supports HEIC per this trac issue and this Make Core post. In March 2025, I was able to upload HEIC images and have them converted in this post without any errors. As of today, when I try to upload HEIC images, I am running into trouble:

1. In the editor, the upload fails and I am shown a snackbar notice of "The web server cannot generate responsive image sizes for this image. Convert it to JPEG or PNG before uploading."

2. In the media library, the upload works but shows an error: "This image cannot be displayed in a web browser. For best results convert it to JPEG before uploading." I can then insert the image into my post.

I checked WP 6.8.1 to see if this was a known change with 6.8 for some reason but it doesn't appear to be.

Replication steps

1. Open a post or page.
2. Try to drag and drop a HEIC image into the content.
3. See error.

Site owner impact

More than 60% of the total website/platform users

Severity

Moderate

What other impact(s) does this issue have?

No response

If a workaround is available, please outline it here.

The main workaround I can find (that still results in an error) is to open the media library and upload the HEIC image there. The upload will complete and you can then insert.

Platform

Simple, Atomic