Generic-RAW

Digital Camera Raw (Generic Linux MIME)

image/x-dcraw Released 1997 · by freedesktop.org (MIME mapping) / Dave Coffin (dcraw tool)

The image/x-dcraw MIME type is a generic, 'super-class' alias established by the freedesktop.org shared-mime-info specification to broadly represent digital camera raw image files. It is named after `dcraw`, the legendary open-source ANSI C program written by Dave Coffin that pioneered open decoding for dozens of proprietary raw formats. Today, this MIME type is used primarily by Linux desktop environments (like GNOME and KDE) and server applications (like Nextcloud) as a fallback identifier for unrecognized raw sensor data before it can be mapped to a specific vendor's MIME type (e.g., image/x-canon-cr2 or image/x-nikon-nef).

Photography & Raw Imaging ✦ HDR Production Ready

Technical Specifications

MIME Type

image/x-dcraw

Extensions

.raw

Container

Varies (Predominantly TIFF/EP)

Compression

Lossless & Uncompressed

Algorithms

Varies (Often Lossless JPEG ITU-T81 or uncompressed)

Color Depth

12-bit, 14-bit, 16-bit

Metadata

EXIF XMP ICC

Capabilities

Transparency

Animation

Progressive Loading

Alpha Channel

HDR Support

Official Specification

Aliases: image/raw

Magic Bytes & HTTP Headers

File Signature (Magic Bytes)

Varies by vendor format

ASCII: None

HTTP Headers

Content-Type: image/x-dcraw

HTML Accept Attribute

accept="None"

Browser Support Matrix

Browser	Status	Min Version
Chrome	Not Supported	—
Firefox	Not Supported	—
Safari	Not Supported	—
Edge	Not Supported	—
Internet Explorer	Not Supported	Legacy

Advantages & Limitations

Advantages

Provides a unified, highly useful catch-all MIME type for application developers who just need to know if a file is a raw image, rather than tracking 50+ individual camera extensions
Deeply integrated into the Linux desktop ecosystem, ensuring file manager thumbnails work seamlessly via tools like ufraw-thumbnailer

Limitations

Not an official IANA standard
Can cause conflicts where standard TIFF files are misidentified as raw camera data by over-aggressive MIME sniffers
The underlying 'dcraw' tool was abandoned by its creator in 2018 (though its successor, LibRaw, continues to maintain the ecosystem)

Developer Code Snippets

import mimetypes
# On Linux systems utilizing the shared-mime-info database, querying a generic raw extension may return this type.
print(mimetypes.guess_type('photo.raw')[0]) # May output 'image/x-dcraw'

const mime = require('mime');
// Many JS MIME libraries do not map x-dcraw by default as it is Linux-specific, but it can be manually registered.
mime.define({'image/x-dcraw': ['raw']});
console.log(mime.getType('photo.raw'));

import (
    "net/http"
    "os"
)
// Go's native http.DetectContentType will not return image/x-dcraw. It will likely resolve underlying TIFF headers to 'image/tiff'.

$mime = mime_content_type('photo.raw');
echo $mime; // On Debian/Ubuntu servers, the fileinfo extension using system magic databases will frequently output 'image/x-dcraw' for unrecognized RAWs.

File Detection Steps

How to programmatically detect a image/x-dcraw file by reading its raw bytes:

1 This MIME type does not have its own specific magic byte signature, as it acts as an umbrella class.
2 In the freedesktop.org shared-mime-info XML database, image/x-dcraw is configured as a super-class (often subclassing image/tiff). Individual formats like image/x-canon-cr2 or image/x-nikon-nef are then subclassed beneath it.
3 If a sniffer identifies raw sensor data but cannot match the specific proprietary camera vendor tag, it will gracefully fall back to returning image/x-dcraw.

Software Support

d

dcraw / LibRaw

D

Darktable

R

RawTherapee

G

GNOME / KDE File Managers

Conversion Tools

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JSON API

All data on this page is available as a free, open JSON API. Use it in your project, documentation, or tooling.

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Frequently Asked Questions

What is an image/x-dcraw file?

It is not a specific file format. Rather, image/x-dcraw is a generic MIME type used primarily by Linux operating systems to classify dozens of different digital camera raw formats (like CR2, NEF, ARW, and DNG) under one umbrella category.

What does 'dcraw' stand for?

dcraw (Dave Coffin's raw) is an open-source command-line tool written in ANSI C that became the foundation for almost all open-source raw image decoders (including LibRaw, UFRaw, and Darktable). The Linux community adopted its name to represent the entire category of files it could process.

Why does my Nextcloud server show image/x-dcraw instead of image/tiff?

Many raw formats (and some standard TIFFs) share the same underlying TIFF byte structure. Automated file sniffers relying on the freedesktop.org database often use image/x-dcraw as a fallback for any complex TIFF-like file that appears to contain raw camera sensor data.