Canon CR3 MIME Type

What does image/x-canon-cr3 mean?

The image/x-canon-cr3 media type identifies Canon Raw 3 photographs, normally stored with the .cr3 extension. A CR3 preserves minimally processed camera-sensor measurements plus the metadata a raw processor needs to produce a viewable image. Compared with a camera-finished JPEG, it leaves much more freedom to adjust white balance, exposure, tonal range, noise reduction, and color rendering.

image/x-canon-cr3 is a conventional identifier, not an IANA-registered media type. It does not appear in IANA's current image registry. This matters when exchanging files through systems that accept only registered media types: the .cr3 filename and an explicit application-level agreement may be more dependable than MIME negotiation alone.¹

How is a CR3 file structured and identified?

Unlike the TIFF-based CR2 format, CR3 uses an ISO base media file format container. Its boxes can carry Canon-specific metadata, raw image data, and camera-rendered previews. The format has been documented mainly through reverse engineering rather than a public Canon specification.³⁴

The practical signature is the ftyp box and CR3's crx brand. At byte offset 4, the bytes are:

66 74 79 70 63 72 78
f  t  y  p  c  r  x

The first four bytes before that sequence are the box size, so they vary. A validator must parse the container rather than assume one fixed whole-file prefix. The UK's PRONOM registry uses this ftypcrx pattern and additional container structure to identify CR3 files.⁵

Canon RAW files also include an embedded JPEG so cameras and file browsers can show an immediate picture without developing the sensor data.² That explains why a general viewer can sometimes display a CR3 even though it cannot decode the raw capture. Renaming a .cr3 file to .jpg, .cr2, or .mp4 does not convert it.

When did Canon introduce CR3?

Canon introduced CR3 with the EOS M50 generation in 2018. Canon's EOS M50 manual was dated February 27, 2018, and its specifications describe CR3 as a Canon 14-bit RAW format.⁶ CR3 succeeded CR2, replacing its TIFF-based container with the ISO media container used by CR3.³

The format remains in active use across Canon's mirrorless and recent camera lines. Adobe's current compatibility table lists CR3 output for models ranging from the EOS M50 and EOS R to newer EOS R bodies, with a minimum Camera Raw version for each model.⁷

How to open a .cr3 file

Use a raw processor that supports the exact camera model:

• Canon Digital Photo Professional (DPP) is Canon's own raw developer. Canon lists .CR3 among the RAW formats accepted from compatible cameras.⁸
• Adobe Camera Raw and Lightroom support many CR3-producing Canon cameras. Adobe's table identifies the first Camera Raw release for each body.⁷
• Apple Photos and other system-integrated apps can use Apple's camera-specific RAW support on supported operating-system versions.⁹

Chrome, Edge, Firefox, Opera, and Safari do not natively develop CR3 files as web images. MDN's guide to browser image formats does not list CR3.¹⁰ For a website, publish a rendered JPEG, WebP, AVIF, or PNG, and offer the CR3 separately when visitors need the original.

Support in Poly

Poly recognizes both .cr3 filenames and image/x-canon-cr3. Its CR3 support lets you:

• Browse sharp thumbnails and open the photo in the image viewer.
• Search by filename, available metadata, visual similarity, and color.
• Ask the Poly agent about the photo's visible content.

Poly extracts available Exif metadata but does not demosaic or color-develop the raw sensor samples. It also does not OCR text visible in an ordinary image. The preview may therefore differ from the rendering in DPP or Camera Raw, and the agent cannot assess raw-level highlight recovery, inspect the sensor mosaic, or reproduce a particular developer's color science.

RAW and C-RAW use the same extension

Canon cameras can store both normal RAW and Compact RAW captures in .cr3 files. Canon says ordinary CR3 RAW brightness data is losslessly compressed. C-RAW keeps the camera's full pixel dimensions but reduces the stored information further to make a smaller file.²

Canon's EOS R5 example gives the necessary context for its size figures: on that 45-megapixel camera, Canon reports typical files of about 45.4 MB for RAW and 22 MB for C-RAW. Canon also warns that sizes vary by image and that C-RAW can show more noise when a substantially underexposed photo is brightened.² Those figures describe that camera and workflow, not a universal compression ratio.

Both modes require a camera-aware raw processor. The .cr3 extension alone does not reveal which mode was used, and Poly does not compare or develop their sensor payloads.

Converting CR3 for editing, sharing, or archiving

Choose a destination based on what must survive:

Canon DPP can convert RAW images to JPEG or TIFF and apply the current editing recipe to the exported file.¹¹ Keep the original CR3 after export. A derivative records one interpretation of the capture and cannot reconstruct all of the original sensor measurements later.

What is the difference between CR3 and CR2?

The two formats need different parsers. CR3 is CR2's successor, but it is not a backward-compatible revision of the same container.³