Today’s Question: I’m accustomed to seeing XMP (sidecar) files with the same (base) name as my edited images from Lightroom Classic. I just noticed a file I edited also has an ACR (Adobe Camera Raw?) file. Do I really need this one too or can I delete it?
Tim’s Quick Answer: You should retain both the XMP and ACR files, as they contain details of metadata updates and adjustments you’ve applied to the original raw captures in Lightroom Classic (or Adobe Camera Raw).
More Detail: As many photographers are probably already aware, XMP sidecar files are used by software such as Lightroom Classic and Camera Raw to store metadata that has been updated for raw captures, so that the original raw capture doesn’t need to be modified.
This approach was recently updated to include both an XMP and an ACR sidecar file, in part to help improve performance. The XMP file contains standard metadata updates, such as keywords and star ratings, while the ACR file contains raster data such as masks used for targeted adjustments.
As such, you generally want to preserve both of those files along with the original raw capture. Of course, deleting the XMP and ACR files won’t affect the original capture data in the raw capture file, so it is possible to delete those files without losing the original photo. However, in most cases you would want to retain the metadata updates and adjustments for your photos. In other words, the only reason to delete the XMP and ACR files is if you wanted to effectively reset an image to the original capture right out of the camera with no metadata updates or adjustments.
