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Since the file type of the thumbnails has been changed, the asset streamer returns the response header Content-Type: image/webp instead of the correct response header Content-Type: image/jpeg for existing thumbnails. Most browsers should be able to display the thumbnails despite of this. If it becomes an issue, the existing thumbnails can either be re-generated as described above, or the thumbnail formats can be modified to be of the type jpeg.
Source format
The new transcode system now supports a special SourceFormat that can be used to refer to and get the source files of assets. A special “Original” format of this type is now defined out-of-the-box. If you have previously hard-coded the “Original” format in a list of available download qualities, this can lead to two “Original” formats being shown. It should no longer be necessary to have any special-case handling for getting source formats.