Today’s Question: If I lose XMP sidecar file, does the raw capture file contain that same XMP info?
Tim’s Quick Answer: No, metadata updates are not applied to the original raw capture by software such as Adobe Bridge, Photoshop, or Lightroom Classic. Therefore, if you lost an XMP sidecar file (and your catalog in the case of Lightroom Classic) you would lose the metadata updates and adjustments for that photo.
More Detail: When you apply metadata updates or adjustments to a raw capture, those updates are not actually written to the source raw capture. The idea is that the raw capture represents the original unprocessed image, and you don’t want to risk corrupting that file by making changes to it.
Instead of updating the source raw capture, updates are written elsewhere. In Lightroom Classic by default any updates you apply are only saved within the Lightroom Classic catalog. Other software such as Adobe Bridge or Photoshop will write those changes to an XMP sidecar file automatically. And in Lightroom Classic you can enable an option to automatically write updates to an XMP sidecar file (in addition to the catalog) in the Catalog Settings dialog.
Note, by the way, that the XMP sidecar file is a file with the same base filename as the original raw capture, located in the same folder, but with an “xmp” filename extension rather than the extension used by the raw capture format for your camera.
If you lose an XMP sidecar file for a raw capture, you will lose the metadata updates for that photo. As long as you have the raw capture file, of course, you will still have the photo, just not the metadata without the XMP sidecar file. An exception to this would be with software such as Lightroom Classic, where the metadata is also written to the catalog file.
So for Lightroom Classic users, if you lose an XMP sidecar file for a raw capture, you would still have all of the updates within your Lightroom Classic catalog, and the XMP file could be created again. For photographers using other software, it can be important to protect the XMP sidecar files in addition to your source raw captures.