XMP sidecar
An XMP sidecar is a small text file next to your RAW in which edits and metadata can be stored. Lightroom Classic normally keeps edits in the catalog, but can also write them to XMP so other programs can read them. The XMP file has the same name as your RAW, but the .xmp extension.
Handy if you want to share your edits with other software like Bridge or Camera Raw, or as extra safety alongside your catalog. With DNG files the data is stored inside the file itself, so you don't need a separate sidecar. If you move a RAW, always take the XMP file with it. Tip: turn on 'automatically write changes into XMP' if you like keeping your settings with the files themselves.
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