TL;DR: A sidecar file is a small companion file—almost always an .xmp file written in Adobe's RDF/XML format—that sits in the same folder as a photo and shares its base filename (IMG_2043.CR3 pairs with IMG_2043.xmp). It exists because RAW formats like Canon's CR3, Nikon's NEF, and Sony's ARW are treated as read-only originals, so editors such as Lightroom Classic and Adobe Camera Raw record your develop settings and metadata in the sidecar instead of altering the RAW itself. That sidecar carries XMP and IPTC fields the original may never visibly expose: creator, copyright, captions, keywords, star ratings, and frequently GPS coordinates. It matters because cleaning an exported JPEG does nothing to the sidecar—hand someone the RAW plus its .xmp and all of that metadata travels with it.
If you have ever copied a folder of photos and noticed a second file with the same name but a .xmp extension sitting next to each image, you have already met a sidecar without anyone explaining what it was. Sidecars are quietly everywhere in a photographer's workflow, and most of the time they do their job invisibly. The trouble starts when you assume that cleaning a photo cleans everything attached to it. A sidecar is a separate file with its own copy of sensitive metadata, and it follows its own rules. This guide explains what a sidecar is, why the format exists, what is actually stored inside one, and what that means the moment you want to share or strip a file.
What Is a Sidecar File, Exactly?
A sidecar file—sometimes called a buddy file or a connected file—is a separate file stored alongside a main file to hold data the main file cannot or should not store internally. The name borrows from motorcycle sidecars: a companion that rides next to the original and goes wherever it goes. In photography, that companion is almost always an XMP file.
XMP stands for Extensible Metadata Platform, a standard Adobe introduced in 2001 and serialized as RDF/XML in plain UTF-8 text. That last detail matters more than it sounds: an .xmp sidecar is not an opaque binary blob. You can open it in any text editor and read it. Inside, you will find namespaced tags—crs: for Camera Raw settings, dc: for Dublin Core descriptive fields, photoshop: for editorial data, and exif: for capture data copied from the camera. The file lives in the same directory as the image and carries the same base name, which is how editing software knows the two belong together.
The key thing to hold onto is that a sidecar is genuinely a second file. It is not a hidden section inside your photo. It can be copied, emailed, backed up, or deleted on its own, completely independent of the image it describes. That independence is the source of both its usefulness and its risk.
Why Do Sidecar Files Even Exist?
Sidecars solve a specific problem created by RAW photography. A RAW file—Canon's CR2 and CR3, Nikon's NEF, Sony's ARW, Fujifilm's RAF, Olympus's ORF—is the unprocessed readout from the camera's sensor, and most software treats it as a digital negative: something to preserve untouched. These formats are also proprietary and only lightly documented, so writing new data back into them risks corrupting a structure the camera vendor controls. The safe choice is simply not to modify the RAW at all.
That constraint pairs with how modern editors work. Lightroom, Camera Raw, and Capture One all edit non-destructively—they never change your original pixels. Instead, every adjustment is stored as a set of instructions: crop to these coordinates, raise exposure by 0.7 stops, set white balance to 5400K, apply this masking. Those instructions have to live somewhere. There are only two reasonable places to put them: a central database, or a per-file companion.
Adobe Lightroom Classic uses a central catalog (a .lrcat database) by default, but it can also write a .xmp sidecar next to each proprietary RAW so the edits and metadata travel with the file. Adobe Camera Raw and Adobe Bridge write sidecars by default. The sidecar, in other words, is how your edits and your metadata persist right next to a file without ever touching the original. It is an elegant solution—and it quietly creates a second copy of everything you would later want to clean.
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What's Actually Inside an XMP Sidecar?
A sidecar carries two broad payloads, and only one of them is about your edits.
The first payload is the develop recipe: crop and rotation, exposure and contrast, white balance, the full tone curve, local adjustment masks, lens corrections, and sharpening. This is the part you genuinely want when you reopen a project, and on its own it reveals little about you.
The second payload is the metadata, and this is where privacy enters the picture. A sidecar routinely stores IPTC and XMP descriptive fields: the creator's name, a copyright notice, contact details, a caption, and keywords—both flat and hierarchical, the kind that often spell out a location or a client name. Star ratings and color labels live here too. Critically, sidecars also frequently hold a copy of the camera's EXIF capture data, including the GPS block with the latitude and longitude where the shot was taken. If you want the full background on those overlapping standards, we cover it in IPTC vs EXIF vs XMP: what's the difference, and the camera side specifically in what is EXIF data.
So when you read an .xmp in a text editor and see a exif:GPSLatitude line or a dc:creator tag with your full legal name, that is not a glitch. That is the sidecar doing exactly what it was designed to do—just somewhere you were not looking.
Where Do Sidecar Files Show Up?
The most common source is Adobe Camera Raw and Bridge, which drop an IMG_2043.xmp next to each RAW the moment you adjust it. Lightroom Classic keeps everything in its catalog by default, but turning on "Automatically write changes into XMP" (or pressing Save Metadata to File) produces the same sidecars for proprietary RAW formats. Capture One uses its own variant—.cos settings files kept in a CaptureOne subfolder rather than loose next to the image.
There is one important exception worth remembering. Adobe's DNG format is an open RAW container that can embed XMP inside the file, so a DNG generally has no separate sidecar—its metadata is internal. That single difference changes how you clean it: with a CR3 or NEF you look for a neighboring .xmp, but with a DNG the metadata is baked into the file itself and has to be stripped from within. Sidecars also appear outside photography—video cameras drop .thm and .xmp companions, for example—but the photo workflow is where they matter most for personal privacy.
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The Privacy Problem: Sidecars Carry What Your Export Doesn't
Here is the scenario that catches people. You finish a shoot, export a web-ready JPEG with metadata stripped on the way out, and feel safe. Then you hand the client the folder of RAW files for archival, or you back the project up to a shared drive, or you sync the folder to a collaborator. The JPEG you cleaned is fine. The RAW files came with their .xmp sidecars, and you never touched those.
Because a sidecar is plain text, the person who receives it does not need special tools. They can open IMG_2043.xmp in Notepad or TextEdit and read the GPS coordinates of where you stood, your full name in the creator field, your contact email in the rights block, and any location keywords you tagged. Stripping the export did nothing to prevent that, because the sidecar is a separate file that was never in the export's path. We go deeper into this exact failure mode in delivering RAW files without leaking metadata, and the general habit of cleaning before you share in how to strip EXIF data from a photo.
The lesson is simple to state and easy to forget: cleaning the image is not the same as cleaning the package. If you are sharing originals, the sidecar is part of what you are sharing.
How to Handle Sidecar Files When You Clean Metadata
Treat the photo and its sidecar as one unit. Start by locating the sidecar—it shares the image's base name, so a quick sort of the folder pairs each .xmp with its RAW. Next, decide whether you even need to send the sidecar: if your deliverable is a flattened JPEG or TIFF, you usually should not be shipping the RAW or its companion at all. If you are sharing the originals on purpose, run both the image and the .xmp through a metadata cleaner so the descriptive, rights, and GPS fields come out of both, or delete the sidecar outright when you do not need to pass along your develop settings. For DNGs, remember the metadata is embedded, so strip the XMP from inside the file rather than hunting for a sidecar that isn't there. Command-line users can manage all of this with ExifTool, which reads, writes, and deletes sidecars directly; Metadata Cleaner handles the XMP, IPTC, and EXIF layers in one local pass without uploading anything. Finally, verify: reopen the cleaned files in a viewer and confirm no XMP, IPTC, or GPS tags survived.
What Deleting a Sidecar Does—and Doesn't—Do
Deleting the .xmp removes the companion copy of your metadata and your edits, but it is one layer, not the whole job, and it helps to be honest about the limits. The RAW original still contains the EXIF block the camera wrote into it—make, model, exposure, timestamp, and sometimes GPS—so the sidecar was never the only copy of that data. Your Lightroom catalog still holds everything on your own machine even after the sidecar is gone, which is fine for your privacy but means the data is not truly destroyed locally. Some applications will quietly regenerate a fresh sidecar the next time you open the RAW. And any derivative you already shared is not retroactively cleaned by deleting a file on your disk today.
None of that makes sidecar cleanup pointless—it makes it necessary but insufficient on its own. To actually de-identify a deliverable, clean the embedded metadata inside the file and remove or scrub the sidecar, then confirm the result. Do both, and there is nothing left riding alongside.
The Bottom Line
A sidecar file is a separate companion file—nearly always an .xmp—that sits next to a RAW photo and stores your edits along with a full set of metadata: creator, copyright, keywords, ratings, and often GPS. It exists for a good reason, to keep non-destructive edits and metadata with a file without modifying a proprietary original. But that same design makes it an extra, plain-text copy of your most sensitive metadata, one that survives untouched when you clean only the export. Treat the original and its sidecar as a single package, and clean them together.
Want to be sure nothing is hiding next to your files? Try Metadata Cleaner free to strip EXIF, IPTC, and XMP from your images and sidecars in one private, local pass—no uploads, no leftovers.