How to Enable XMP Sidecars in Lightroom Classic (2026)

Published November 3, 2026 · Daniel Tello · RevelRaw

You copied a shoot to a new folder last night. The pictures open fine. The stars, keywords and careful exposure work don't. That usually isn't corruption. It's a missing partner file, or one that was never written because the edits lived only in the catalog.

This is the step-by-step guide: turn sidecar writing on, prove the files exist, test one frame in the next app and keep the pair intact. For what a sidecar stores and why edits seem to vanish, read XMP sidecar files explained. If you came here for the PC memory setting with the same three letters, skip to the Intel XMP section.

What Does Turning On XMP Do for RAW Photos?

It makes your editor write a small text file with the same name as the camera file, in the same folder. IMG_0001.ARW stays untouched. IMG_0001.xmp sits beside it and carries the ratings, keywords and develop settings. If you only see the first file, the edits haven't left the app yet.

XMP stands for Extensible Metadata Platform, a format Adobe introduced in 2001; Adobe's metadata overview is a plain-language introduction to it. Adobe's XMP specifications describe a data model, a serialization in XML and RDF, and core properties, with Part 1 also published as ISO 16684-1:2012. The same page notes that XMP can be embedded in files such as JPEG and PDF, and that embedding avoids the problems of metadata stored separately.

For RAW, separate storage is the point. The editor writes instructions and never rewrites the sensor data, which is the basis of what RAW photo editing involves and why the original stays reversible.

Rename, move or back up one file without the others, and the RAW still opens. The edits disappear.

How Do You Turn On XMP Writing in Lightroom Classic?

Lightroom Classic keeps edits in its catalog by default. A catalog-only save doesn't count as XMP being on.

1. Open Catalog Settings. On a Mac choose Lightroom Classic > Catalog Settings (Edit > Catalog Settings on Windows), then the Metadata tab.
2. Turn on automatic writing. Tick Automatically write changes into XMP. Lightroom then keeps saving your edits to the sidecars as you work.
3. Force the older frames. If photos you edited earlier still have no .xmp, select them in the Library or Develop module, choose Photo > Save Metadata to File (Cmd-S), and click Continue in the dialog.

Proprietary RAW files get a separate .xmp. DNG, JPEG and TIFF files get the XMP written inside the file instead, so don't look for a sidecar next to those.

How Do You Check That the Sidecar Was Written?

Check twice: once in Lightroom, once on disk. Adobe's Lightroom Classic documentation on XMP and ACR files gives the in-app check: select the photo in the Library module, open the Metadata panel and read the Sidecar Files field.

1. Read the Sidecar Files field. It should list xmp, and also acr if the photo has heavy edits.
2. Look in Finder. You should see one sidecar per RAW with the same stem, such as IMG_0001.NEF beside IMG_0001.xmp.
3. Test the timestamp. On one throwaway frame, change a slider, save metadata again and confirm the .xmp modification time changes.
4. Open the .xmp in TextEdit. An x:xmpmeta block with rdf:RDF inside is proof that writing works.

Why is there an .acr file too?

Starting with Lightroom Classic 15.0, Adobe says Lightroom writes heavy edits, masks and AI settings such as Super Resolution, Distraction Removal and Denoise to an .acr sidecar, keeping the .xmp lightweight. Photos without heavy edits only get the .xmp. The .acr is part of the pair, not leftover clutter: leave it beside the RAW and copy it with the shoot.

Adobe also notes that Lightroom maintains all the sidecars when you move, rename or delete a photo inside Lightroom. Do those jobs in Lightroom rather than Finder and the pair stays matched.

How Do You Test One Frame Before Moving a Whole Shoot?

Treat the first transfer as a compatibility test, not as proof that every slider moved. One frame tells you the truth cheaply.

1. Make a small, varied edit. With automatic writing on, change exposure, set white balance, add a crop, apply a star rating, type a keyword and paint one local adjustment.
2. Force the save. Use Photo > Save Metadata to File and note the sidecar timestamp in Finder.
3. Quit Lightroom. That stops it holding a newer copy only in its catalog.
4. Open the pair in the destination app. Keep the .xmp beside the RAW, then compare the picture and each field one by one.
5. Keep a reference export. Export a JPEG or TIFF from Lightroom for comparison, and never overwrite the originals.

Write a pass or fail line for that frame. Which of exposure, white balance, crop, rating and keywords arrived? Which must you redo? That short list becomes the rule for the whole shoot.

Subset rule: A readable sidecar isn't the same as an identical render.

XMP standardizes the container and core properties, and apps add their own schemas on top. Another editor may read the file and still ignore Adobe's process versions, profiles or camera-specific rendering, and Lightroom's masks and AI edits now sit in the .acr file that most other apps don't read at all. That's a compatibility subset, not a broken sidecar. Standard fields travel best; proprietary tools travel worst.

If the frame passes on the fields you care about, you have a known baseline. If it doesn't, you've lost five minutes instead of an evening's shoot.

Why Don't Edits Match After Copying or Renaming?

Start with the most common miss: hours of edits and no .xmp on disk. Automatic writing was off and nobody saved metadata to file, so the work lives only in the catalog. Work through the rest one row at a time.

A missing file is a writing problem: fix the setting and force a save before you re-edit anything. A stale timestamp is a trust problem: save again, watch the date change, then reopen once. A stem mismatch after batch renaming is a pairing problem. Rename IMG_0001.NEF to Wedding_001.NEF and leave IMG_0001.xmp behind, and the next app sees a clean negative; rename both or restore the pair from backup.

When a JPEG's embedded metadata disagrees with the RAW's sidecar, keep the sidecar as the RAW instructions and the embedded packet as that export's record. A photo metadata editor workflow shows which values each file actually carries.

Change one cause, recheck the timestamp and reopen once. Change three things at once and you won't know what repaired the pair.

How Do You Keep the RAW and XMP Pair Intact?

Good sidecar habits are boring, which is why they work. Keep one folder per shoot, and treat each RAW with its .xmp and any .acr as one unit when you copy to an SSD, a client drive or a second Mac. If you sort by extension before copying, you'll eventually leave a partner behind.

Back up that folder, not the catalog alone. A catalog the next app can't open isn't a handoff. The folder is.

• Spot-check three stems: after any rename or ingest tool, confirm three RAW and sidecar pairs still match exactly.
• Copy folders, not files: select the shoot folder, never the RAWs alone.
• Leave originals unmodified: a bad sidecar can be deleted and the photo re-edited only if the camera file is untouched.

Export settings aren't develop instructions. Color space, size and file format are chosen when you export, and the exported JPEG, TIFF or HEIF carries its own embedded metadata, separate from the sidecar that stays with your RAW.

A RAW without its sidecar is a clean negative, not a finished edit.

Before you archive a shoot: pair present, names matched, both files in the backup, export metadata chosen on purpose, originals untouched.

How Do You Open the Tested Shoot in RevelRaw?

We make RevelRaw, a native RAW editor for Macs with macOS 26 or later on Apple M1 or later. Copy the whole shoot so every camera file keeps its .xmp beside it, then open that folder. RevelRaw reads supported Lightroom adjustments, including the crop rectangle and straighten angle, from a DNG or an accessible XMP sidecar beside the RAW. It doesn't import the Lightroom catalog, masks or Adobe profiles, and rendering can differ. That's the practical payoff of turning XMP on, and one test worth running when choosing RAW processing software.

1. Open the test frame first. You already know its pass and fail list.
2. Verify crop, straighten and tone. Compare against your reference export before you touch the rest of the shoot.
3. Rebuild what didn't arrive. Recreate masks with RevelRaw's own masks (up to three layers per photo, free) instead of expecting the sidecar to carry them.
4. Choose a look last. AI scene detection ranks 50+ looks for the photo, but only after the transferred crop and tone are confirmed.

That order matters. Looks applied before verification hide transfer problems; applied after, they're a clean creative choice. Ratings go the other way too: stars you set while culling in RevelRaw are written to the RAW's .xmp sidecar, where other apps that read XMP ratings can pick them up.

Opening, editing and comparing unlimited photos is free, including syncing edits across a shoot, and one full-quality export is included. Pro adds unlimited and batch export, as an auto-renewing subscription or a one-time lifetime purchase. Processing happens on your Mac with no account; downloading the app, buying Pro and the one-time Apple selection-model download for click-to-select masks need internet.

If a supported RAW still misreads, note the macOS version, camera body and RAW format before you write to support. Those three details speed up any diagnosis.

What If You Meant Intel XMP Memory Profiles?

Intel XMP (Extreme Memory Profile) has nothing to do with photo metadata. It's a set of memory settings in a Windows PC's BIOS, and Macs don't expose it. Intel's Extreme Memory Profile page describes the profiles as preset combinations of speed, timing and voltage that overclock compatible DDR4 and DDR5 memory, and its footnote warns that altering clock frequency or voltage may void product warranties and reduce stability.

Check support before you change anything. Intel's XMP support guidance for its NUC computers says not all of them support XMP, and lists the checks: the product's technical specifications, whether the memory modules are XMP, and Intel's compatibility tool. Board makers may use another name for the feature, so check the manual.

1. Record your current settings. Write down memory frequency and voltage first.
2. Enter the BIOS. TechRadar's XMP overview (2025) says the start-up key is typically F1, F2, F10, F12 or Delete, depending on the motherboard maker. If that doesn't work, use a guide to find your PC's BIOS hotkey from Windows 11.
3. Enable one profile only. Don't change timings or voltage at the same time, then save and exit.
4. Check and test. Compare the reported values against the memory's rating, then run a memory test before trusting the machine with real work.

A successful boot only proves the machine started once. If tests fail, go back to your recorded settings.

Frequently Asked Questions

How do I enable XMP sidecars in Lightroom Classic?

Open Lightroom Classic > Catalog Settings (Edit > Catalog Settings on Windows), choose Metadata and tick Automatically write changes into XMP. For photos edited before that, select them and choose Photo > Save Metadata to File. Lightroom then writes a same-name .xmp file beside each proprietary RAW file.

Why is there no .xmp file next to my RAW photo?

Usually automatic XMP writing was off and the metadata was never saved to file, so the edits exist only in the catalog. DNG, JPEG and TIFF files never get a separate sidecar because Lightroom writes XMP inside them. If the RAW was copied on its own, the sidecar was simply left behind.

What is the .acr file next to my RAW and .xmp files?

Since Lightroom Classic 15.0, Lightroom writes heavy edits, masks and AI settings such as Super Resolution, Distraction Removal and Denoise to an .acr sidecar, keeping the .xmp small. Keep it beside the RAW and copy it with the shoot, or those edits won't come back in Lightroom.

Is XMP in photo editing the same as Intel XMP in the BIOS?

No. Photo XMP is Adobe's Extensible Metadata Platform, a metadata format stored in sidecar files or inside images. Intel XMP (Extreme Memory Profile) is a set of memory overclocking settings in a PC's BIOS, and Macs don't expose it.

Can RevelRaw read my Lightroom XMP sidecars?

RevelRaw reads supported Lightroom adjustments, including the crop and straighten angle, from a DNG or an accessible XMP sidecar beside the RAW file. It doesn't import the Lightroom catalog, masks or Adobe profiles, and rendering can differ. It requires macOS 26 or later on an Apple M1 or later Mac.

Bring your tested folder, RAW and .xmp together, to RevelRaw: a native Mac editor that reads supported Lightroom adjustments from sidecars on your Mac, with no RevelRaw account. Editing is free and the first full-quality export is included, so you can run the one-frame test on your own shoot. It requires macOS 26 or later on an Apple M1 or later Mac.