---
title: "Sidecar file — Glossary | LLMind"
description: "A separate file (often .xmp) that stores metadata for a primary file, rather than embedding metadata inside it."
url: https://llmind.org/glossary/sidecar-file/
source_format: html
---
[← Glossary](https://llmind.org/glossary/)

# Sidecar file

**A separate file (often .xmp) that stores metadata for a primary file, rather than embedding metadata inside it.**

A sidecar file is a companion file that holds metadata for a primary file. If you have a raw camera image `photo.raw`, a sidecar file might be `photo.raw.xmp` or `photo.xmp`. The sidecar is a separate, parallel file in the same directory. Photo editing software like Adobe Lightroom, Capture One, and Darktable use sidecars extensively — they leave the original file untouched and record edits and metadata in a separate .xmp file.

## Why sidecar files exist

Many file formats historically did not support embedded metadata. RAW image formats from cameras (Canon CR2, Nikon NEF, Sony ARW) are proprietary and not designed for metadata injection. Rather than fork these formats or demand their specification, tool makers ship metadata in a companion .xmp file next to the image. The file system keeps them associated; the editor manages both.

## The portability problem

Sidecar files decay when files are copied, renamed, reorganized, or uploaded. Move a photo from your computer to a cloud service or send it via email without the sidecar, and the metadata is lost. Rename `photo.raw` to `photo_final.raw` without updating the sidecar name, and the editor can't find the metadata. Sidecar metadata is fragile because it relies on file naming and directory structure.

## LLMind's answer

LRFS embeds metadata in the XMP packet inside the file itself. When the file moves, the metadata moves with it. No risk of separation, no fragile file-naming conventions. The downside is that some formats (like RAW) may not support embedding. In those cases, a sidecar is still necessary — but LRFS is optimized for formats that do support XMP.

## Related terms

-   [Embedded metadata](https://llmind.org/glossary/embedded-metadata/)
-   [XMP](https://llmind.org/glossary/xmp/)
-   [Self-describing file](https://llmind.org/glossary/self-describing-file/)

## See also

-   [Semantic layer for files](https://llmind.org/learn/semantic-layer-files/)
-   [Spec](https://llmind.org/spec/)