What Is an XMP Sidecar?
Reviewed 2026-07-19 · by the Cull AI Studio team
An XMP sidecar is a small text file that sits next to an image file, usually a RAW file, and stores metadata about it: star ratings, color labels, flags, and other information. Because the metadata lives in the sidecar rather than inside the RAW file, the original stays untouched, and any software that understands XMP, including Lightroom, can read those ratings and labels when it imports the photos.
Why sidecars exist
RAW files are proprietary camera formats, and writing new data into them is risky and often impossible to do safely. The industry’s answer is the sidecar: keep the pixels in the RAW file, keep the opinions about the pixels in a companion .xmp file with the same name. IMG_4021.CR3 gets an IMG_4021.xmp, and together they carry both the image and its metadata.
What lives in a sidecar
- Star ratings (0 to 5).
- Color labels (red, yellow, green, and so on).
- Pick and reject flags.
- Keywords, copyright, and other descriptive metadata.
- Develop settings, when written by editing software.
Why culling tools use them
Sidecars are the lingua franca between a culling pass and an editing catalog. When a culling tool writes its verdicts as ratings and labels in XMP, your editor imports the folder and the cull is simply there: filter to five stars and edit. No proprietary catalog format, no re-marking a few thousand frames by hand, and no bottleneck feeding a slow in-catalog culling session. It is also inherently non-destructive: delete every sidecar and your RAW files are exactly as the camera wrote them.
Limitations
A sidecar is a separate file, so it must travel with its image; copy the RAW without the .xmp and the ratings stay behind. Some software reads XMP only at import time, so metadata written after import may require an explicit re-read. And formats that support embedded metadata, like JPEG and DNG, sometimes store it internally instead, so a mixed-format shoot can carry metadata in two different places.
How Cull AI Studio handles this
Cull AI Studio writes its cull results as XMP sidecars next to your files: keepers are rated five stars with a green label, rejects one star with red, and review frames get a yellow flag. Lightroom reads them on import, so the cull flows straight into your normal editing workflow without installing anything extra. The sidecars are generated locally, like everything else in the app, since all processing stays on your computer, and your originals are never edited, only accompanied. Sorted output folders and a copy-or-move choice come along with the sidecars, as described in what wedding photo culling software does.
Frequently asked questions
Does an XMP sidecar change my RAW file?
No. The RAW file is never modified; all ratings, labels, and flags live in the separate .xmp file beside it.
Will Lightroom read the sidecars automatically?
Yes, Lightroom reads XMP sidecars when it imports the files, so ratings and labels from a cull appear in the catalog without extra steps.
What happens if I move photos without their sidecars?
The metadata stays behind with the orphaned .xmp files. Always move a RAW and its sidecar together, or let your software handle the move.
What does Cull AI Studio write into sidecars?
Keepers get five stars and a green label, rejects get one star and red, and review frames get a yellow flag, written next to the files for your editor to read on import.
Try it on a real wedding
The honest test is your own shoot: import a real wedding, let Cull AI Studio sort every frame into KEEP, REJECT, and REVIEW on your own computer, and see how well it fits your workflow. 7-day free trial, full features, cancel anytime during the trial — and your photos never leave your computer.
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