All about CR3 files

CR3 stands for Canon RAW 3 and is the latest RAW image format used in Canon digital cameras. It was introduced in 2018 with the Canon EOS M50 and replaced the older CR2 format. Like other RAW formats, CR3 files contain not only the unprocessed image data but also extensive metadata regarding exposure, white balance and camera settings.

Technical structure

CR3 is based on the ISO Base Media File Format and thus uses the same container as MP4 files. Its predecessor, CR2, was still based on the TIFF standard. For compression, CR3 uses Canon’s proprietary CRX codec. This combines techniques from JPEG-LS (Rice-Golomb coding) and JPEG-2000 (LeGall 5/3 wavelet transformation). As a result, CR3 files are significantly smaller whilst offering the same or even better image quality than CR2.

But why go to all this trouble with compression?

At first glance, more efficient compression seems unnecessary, as memory cards with over 1TB of storage have long been standard, and the internet for exchanging data is also much faster than it was when CR2 was introduced. But the real bottleneck lies in write speed. Modern cameras such as the EOS R5 generate data streams of just under 2GB per second of raw footage at 30 frames per second. Even fast CFexpress cards cannot sustain these write speeds for long. After a few seconds, the internal buffer would be full and the camera would pause.
CR3 can reduce file size by approximately 40%. This means: more images in the buffer, faster clearing and thus longer continuous shooting without interruption. In many situations, such as sports, wildlife or event photography, this can make the difference between a shot taken and one missed.

CR3 compression modes

CR3 supports two compression modes:

• RAW: Lossless compression, maximum image quality
• C-RAW (Compressed-RAW): Lossy compression, approx. 40% smaller with minimal visible loss of quality

C-RAW is particularly useful for photographers dealing with high volumes of images, such as at sporting events or weddings. Precisely where a missed moment cannot be recaptured. Continuous shooting generates large amounts of data that need to be written to the card quickly.

The history of Canon RAW formats

Over the years, Canon has developed three generations of RAW formats, which I have listed in the table below:

The switch to ISO BMFF CR3 has been the biggest technical leap. The format has a modular structure, the container supports streaming and is therefore future-proof for even higher resolutions and fast continuous shooting rates.

Sources

Laurent Clévy: Canon CR3 Format Documentation (GitHub)
Archive Team: Canon RAW 3
ISO/IEC 14496-12: ISO Base Media File Format

Last updated on 17. March 2026 by Sören with the experience of more than 127,975,646 converted files since 2013.