The CR2 file (.cr2)

CR2 is the raw format of a generation of Canon EOS cameras. It replaced Canon's first raw format, CRW, in cameras such as the EOS 20D and EOS 350D (Digital Rebel XT), from 2004. In 2018, starting with the EOS M50, Canon began replacing it with CR3. So most Canon DSLR photos shot in RAW from the mid-2000s to the late 2010s are CR2 files.

Unlike CRW, CR2 is built on TIFF. That made it easier for other software to read the previews and metadata, but the raw image itself still needs a decoder that knows Canon's way of storing it, and a raw converter needs colour data for each camera model.

A CR2 is a working file, not a finished photo. To share a picture, develop it and export a JPG.

A Canon sensor records one colour per pixel through a grid of red, green and blue filters. A CR2 keeps those single-colour values at 12 or 14 bits each, before the camera has filled in the missing colours (demosaicing), set the white balance, applied the picture style and tone curve, sharpened and reduced noise. All of that happens later, in raw software, and can be changed at any time without losing quality.

• It looks flat or different. Raw software starts from its own neutral rendering, not Canon's picture style. Canon's Digital Photo Professional is the one app that reproduces the camera's styles exactly; others use profiles that imitate them.
• It looks fine, then changes. Many viewers first show the embedded JPEG preview, then replace it with their own rendering of the raw data.
• More room to edit. Highlights and shadows that a JPEG would have clipped are often still there, and white balance can be changed freely.

Many CR2 cameras offered smaller raw options besides full-size RAW, called M-RAW and S-RAW (also mRAW and sRAW). They are still .cr2 files, but they hold fewer pixels, and the data isn't stored as one colour per pixel: it's already partly processed, stored as brightness and colour (YCbCr) values.

Some raw converters and older tools handle M-RAW and S-RAW less well than full RAW. If you want to keep everything the sensor recorded, use full-size RAW. CR3 cameras offer C-RAW instead, a smaller raw option that keeps the full resolution.

Converting CR2 to DNG with Adobe's free DNG Converter keeps the raw data and makes the file readable by any DNG-capable software. Canon's own software won't open the DNG, though, so keep the originals if you use Digital Photo Professional.

• Canon's own software: Digital Photo Professional (DPP) is free for Canon owners from Canon's support site, for Windows and macOS. It reproduces the camera's picture styles and lens corrections.
• Other editors: Lightroom, Photoshop (Camera Raw), Capture One, DxO PhotoLab, Affinity Photo, and the free darktable and RawTherapee all read CR2.
• Mac: Photos and Preview open CR2 files from the Canon models on Apple's supported RAW list, which includes many EOS cameras.
• Windows: install Microsoft's free Raw Image Extension from the Microsoft Store. It's built on the open-source LibRaw library and adds CR2 thumbnails in File Explorer and viewing in Photos.
• Phones: Lightroom mobile and other raw editors open CR2 on iOS and Android; iPhones and iPads also open supported Canon models in Photos.

# CR2 to JPEG with darktable or RawTherapee
darktable-cli IMG_0001.CR2 IMG_0001.jpg
rawtherapee-cli -o IMG_0001.jpg -c IMG_0001.CR2

# just pull out the camera's full-size JPEG preview, no processing
exiftool -b -PreviewImage IMG_0001.CR2 > IMG_0001_preview.jpg

Extracting the preview is quick and gives exactly what the camera showed, but it's an 8-bit JPEG with the camera's settings baked in; you lose the raw latitude.

• The software is older than the camera. Raw converters need specific support for each camera model, even within one format. A CR2 from a camera released after your version of Lightroom, Photoshop or an older Photos app may not open. Update the software, or convert the files with the latest free Adobe DNG Converter and open the DNGs instead.
• Only a small or blurry picture appears. The viewer can't decode the raw data and is showing the embedded thumbnail or preview.
• It opened in DPP but not elsewhere after editing. Canon's software stores its edits inside the CR2, and some other programs have reportedly failed to read files changed this way. Keep an untouched copy of the originals.
• The file is corrupt. Raw files copied from a failing card often show coloured bands or a half-grey image. Try copying again with a card reader; the embedded JPEG preview may still be extractable with exiftool -b -PreviewImage.

A CR2 carries everything a camera JPEG does, plus Canon's maker notes:

• Camera and lens serial numbers, which link every photo to the same body and lens.
• Owner name, artist and copyright, if set in the camera menu.
• GPS location, when the camera has a GPS unit or receiver attached, or takes location from a paired phone.
• Date, time and all settings, including the autofocus points used.

When sharing photos publicly, share an exported JPEG with metadata removed, not the CR2. exiftool -a -G1 IMG_0001.CR2 shows what's in a file.