XMP sidecar
An XMP sidecar is a small .xmp file saved next to a RAW photo that holds its edits, rating, keywords and other metadata without changing the RAW itself.
XMP (Extensible Metadata Platform) is the metadata format Adobe created and most photo software now reads. JPEG, TIFF and DNG files can hold XMP inside them. Proprietary RAW files such as CR3, NEF and ARW are usually left untouched, so software writes their XMP to a separate file with the same name and a .xmp extension — the sidecar.
Keep the pair together and any program that reads XMP sees the same rating, keywords and adjustments.
How it works
When you rate, keyword or edit a RAW file in Lightroom Classic with XMP writing on, or in Bridge or Capture One with sidecar support, the software saves a small text file such as IMG_0042.xmp beside IMG_0042.CR3. The sidecar holds standard fields — star rating, labels, IPTC caption and keywords — plus that program's own edit settings. Rename or move the RAW without the sidecar and the link is lost.
An example: switching editors
A photographer culls a wedding in Photo Mechanic, which writes ratings and captions to sidecars, then imports the folder into Lightroom Classic. Because the sidecars sit next to the RAW files with matching names, the ratings and captions appear in Lightroom without re-doing anything.
Sidecars and CloudTether
Cameras don't usually create sidecars; Canon and Nikon write in-camera ratings into the image file itself. CloudTether transfers the files the camera writes, at full size by default with their own names, so in-camera ratings travel inside the file. Sidecars appear later, when your editing software creates them on the computer. Keep original file names so files you deliver still match sidecars you create from the card.
Embedded or sidecar?
JPEG and DNG carry XMP inside, which is tidy but changes the file. Sidecars leave RAW files untouched, which many photographers prefer for archives — at the cost of keeping two files together.
Tips and common mistakes
- Copy and back up sidecars with their RAW files.
- Don't rename RAW files outside your editor, or sidecars get orphaned.
- Turn on automatic XMP writing if you use more than one program.
See also
Put it into practice
CloudTether tethers your camera to your phone and delivers every shot to the cloud, live as you shoot — no laptop.