CRW File (.crw): What It Is and How to Open It

The basics

What is a CRW file?

CRW is the first of Canon's three raw photo formats. It was used in the early 2000s by Canon's first digital SLRs, the EOS D30, D60, 10D and 300D (Digital Rebel), and by high-end compacts: the PowerShot G1 to G6, S30 to S70 and Pro1. From 2004, Canon's new cameras switched to CR2, and in 2018 to CR3.

The container is CIFF, the Camera Image File Format. Canon released its specification in 1997 and also used CIFF to carry metadata inside some JPEGs. The specification covers the container, not the compressed raw data inside, which other software had to work out by reverse engineering. Canon itself no longer uses CIFF.

Today most CRW files are in old photo archives. They hold the same kind of data as any raw file: the sensor's values before demosaicing, white balance and the camera's processing, so they can still be developed with modern tools, often with better results than the software of the time.

Anatomy

What's inside a CRW file

A CRW file is not TIFF-based, unlike most raw formats. It uses CIFF, Canon's own container: a short header, then one block whose directory sits at the end and points back to the data before it. This outline comes from ExifTool's CRW documentation (based on Canon's CIFF specification and ExifTool's own research), PRONOM's signature and the Library of Congress's camera raw description. Only the 26-byte header has fixed values; no real file is shown.

photo.crw (structure outline)

photo.crw: layout of a Canon CIFF raw file (no real file shown)

offset  bytes                      part
0       49 49                      "II": little-endian byte order
2       1A 00 00 00                header length: 26 bytes
6       48 45 41 50 43 43 44 52    "HEAPCCDR": the CIFF signature
14      02 00 01 00                version 1.2 (0x00010002)
18      00 00 00 00 00 00 00 00    reserved
26      root block, to the end of the file:
          value data               the records' contents, written first
            2005 RawData             the raw sensor data, most of the file
            2007 JpgFromRaw          a JPEG preview (2048 × 1360 on a 300D)
            2008 ThumbnailImage      a 160 × 120 JPEG
            300A ImageProps          a sub-block with the same layout:
              ImageDescription, CameraObject, ShootingRecord,
              MeasuredInfo, ExifInformation …
          directory count          2 bytes
          directory entries        10 bytes each: tag, size, offset
          last 4 bytes             where the directory starts

149 49
Byte order
II, Intel order: numbers are little-endian. ExifTool notes it has only seen this order in CRW files.
21A 00 00 00
Header length
26 bytes. The root block starts right after the header.
348 45 41 50 43 43 44 52
The signature
HEAPCCDR. CIFF calls its blocks heaps; the same structure inside a JPEG's APP0 segment, which some Canon cameras wrote, is marked HEAPJPGM instead.
402 00 01 00
Version
A 32-bit number, 0x00010002: major version 1, minor version 2.
5value data
Data first
The block starts with the contents of its records: the raw image, the previews and the metadata sub-blocks. Records are padded to an even number of bytes.
62005 RawData
The raw image
The sensor values in Canon's own compressed encoding, which isn't part of the CIFF specification. Open-source decoders read it thanks to reverse engineering.
72007 JpgFromRaw, 2008 ThumbnailImage
Previews
A large JPEG preview and a 160 × 120 thumbnail. Even when the raw data can't be decoded, these can often be extracted.
8300A ImageProps
Metadata
A sub-block with the same layout as the root, holding more sub-blocks: camera details, shooting settings, measured exposure and Exif-style information. Each tag number also encodes the kind of data (text, 16-bit or 32-bit numbers, a sub-block).
9last 4 bytes
Directory at the end
Each block ends with the offset of its directory: a 2-byte count, then 10-byte entries giving tag, size and offset (relative to the start of the block). A reader starts at the end of the file and works backwards.

Raw data

What's in the raw data, and why it looks flat

The sensor in a CRW camera records one colour per pixel through red, green and blue filters, 12 bits per pixel on the EOS models: 4,096 levels, against 256 in a JPEG. Raw software fills in the missing colours (demosaicing), sets white balance, converts the colours and applies a tone curve.

It looks flat or dull. That's the raw data with neutral processing, before contrast and saturation are added. Apply an auto-tone or a camera profile.
It looks different from 20 years ago. Modern converters demosaic, reduce noise and handle colour differently from Canon's software of the time. Usually better, sometimes just different.
Only a small picture shows. The viewer can't decode the raw data and shows the embedded JPEG preview instead.

Comparison

CRW vs CR2, CR3 and DNG

	CRW	CR2	CR3	DNG
Years	Early 2000s	2004 to late 2010s	2018 onwards	2004 onwards
Container	CIFF (Canon)	TIFF-based	ISO base media (like MP4)	TIFF-based
Signature	`II` + `HEAPCCDR`	TIFF header + `CR`	`ftypcrx`	TIFF header + DNGVersion tag
Documentation	Container spec from 1997; raw data reverse-engineered	Reverse-engineered	Reverse-engineered	Public, ISO 12234-4

How to

How to open and convert a CRW file today

Mac: Photos and Preview open CRW files from the EOS D30, D60, 10D and 300D, which are still on Apple's supported RAW list.
Windows: Microsoft's free Raw Image Extension is built on LibRaw, the library most open-source tools use for old raw formats; install it and try Photos. Otherwise use one of the editors below.
Edit: Lightroom and Photoshop (Camera Raw), and the free darktable and RawTherapee, all develop CRW.
Canon's software: ZoomBrowser EX and early versions of Digital Photo Professional read CRW. Current Canon software is aimed at newer cameras, so check that it lists your model.

terminal

# develop a CRW to JPEG
darktable-cli CRW_0001.CRW CRW_0001.jpg

# pull out the embedded JPEG preview, no raw decoding needed
exiftool -b -JpgFromRaw CRW_0001.CRW > CRW_0001_preview.jpg

# show what's inside
exiftool -a -G1 CRW_0001.CRW

For old archives

If you keep a folder of CRW files, consider converting copies to DNG with the free Adobe DNG Converter while software support is still good. DNG is openly documented and an ISO standard, so it's a safer long-term bet than a format no camera has written for two decades. Keep the originals as well.

Troubleshooting

Common problems with CRW files

"Unsupported file" in a modern app. Some newer or simpler apps support only CR2 and CR3. Use one of the tools above, or convert to DNG.
Files from a CD or old drive won't open at all. Check the size: a CRW from these cameras is several megabytes. A file of a few kilobytes, or one full of zeros, was damaged in copying; try exiftool -b -JpgFromRaw to rescue the preview.
Wrong date or time. A camera clock that was never set, or reset after a battery change, records wrong dates. exiftool "-AllDates+=1:0:0 0:0:0" folder/ shifts every file in a folder by a year, for example.

Privacy

Privacy: what's recorded in a CRW

These cameras had no GPS, so CRW files don't carry a location unless software added one later. They do record the date and time, all exposure settings, the camera model and, on EOS models, the camera's serial number and the owner name if one was set in the camera. Check with exiftool -a -G1 before publishing old raw files, and share exported JPEGs instead.

Sample files

There are no sample CRW files on this page. Raw files come straight from the camera, so the only real test files are ones shot on an early-2000s Canon such as the EOS 10D or 300D.

Put it online

Have a CRW file? Give it a link.

Drop a CRW on 99helpers and it gets its own web address, useful for sending an old raw photo to someone who can develop it. Browsers can't display raw files, so the file downloads when the link is opened.

Put a CRW file online

Questions

CRW files, frequently asked

What is a CRW file?

A raw photo from an early-2000s Canon camera such as the EOS 10D, EOS 300D or a PowerShot G model, in Canon's CIFF format.

How do I open a CRW file?

On a Mac, Photos or Preview. Otherwise use Lightroom, Photoshop (Camera Raw), darktable or RawTherapee; on Windows, try Photos with Microsoft's Raw Image Extension.

How do I convert CRW to JPG?

Develop it in a raw editor and export as JPEG. For a quick copy of the camera's own preview, run exiftool -b -JpgFromRaw file.CRW > preview.jpg.

What's the difference between CRW and CR2?

CRW uses Canon's CIFF container and came first; CR2, from 2004, is based on TIFF. Both hold raw sensor data with JPEG previews.

Should I convert CRW files to DNG?

For an archive it's a good idea: DNG is openly documented, and the free Adobe DNG Converter reads CRW. Keep the originals too.

Can I still open CRW files in Canon's software?

Canon's software of the time read them. Current versions focus on newer cameras, so other raw editors are usually the easier choice.

Related formats

Other file types explained

CR2 file CR3 file DNG file TIFF file JPEG file RAW file All file types

Keep going

Host a CRW file

Put an old Canon raw photo online at its own address.

Share a CRW file

Send raw files as a link instead of an attachment.

Hosting guides

How to put files, reports and sites online.

Sources

Last reviewed 27 October 2026.