What is a CR3 file?

CR3 is a container: a wrapper that holds streams encoded by something else. It stores a grid of pixels, so enlarging it past its own resolution softens it. It is used for photography and editing.

The extension is .cr3, and the full name is Canon Raw 3. Both matter less than what the file can hold, which is what the rest of this page is about.

Canon published it in 2018. It comes out of Canon EOS R mirrorless bodies and recent DSLRs bodies.

Age is worth knowing here for one practical reason: the older a format is, the more programs have had time to learn it.

Reading it outside the vendor’s own software depends on work done by other people, usually by inspection rather than by documentation. That mostly works and occasionally does not, which is the reason to convert anything you intend to keep.

CR3 stores its content exactly. Saving it again changes nothing, so it can be opened, edited and re-saved as often as you like without accumulating damage — which is what makes it a working format rather than a delivery one.

CR3 has nowhere to record transparency. Anything transparent in the source is filled with a solid colour on the way in — white, unless something chooses otherwise.

Up to 14 bits per channel. It can work in RGB.

More than eight bits per channel is what stops a gradient from stepping when it is edited, which is why it matters in a working file and rarely in a finished one.

Adobe Lightroom and Canon Digital Photo Professional read it, and so do most programs of the same kind.

If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.

No browser reads it.

That is the single most common reason to convert it: not that the format is bad, but that the place you want to show the file cannot read it.

CR3 can hold EXIF, XMP and GPS coordinates.

The GPS coordinates are the field worth thinking about before sending a file anywhere: they say where the photograph was taken, and almost nothing warns you that they are still in there.

CR3 is meant to be opened and changed. Keep the file in this format for as long as the work is going on, and export from it whenever a finished copy is needed.

The recurring complaints: programs often show an embedded preview rather than the real data and support outside its home ground is uneven.

None of these is a reason to avoid the format. They are the things worth knowing before you are surprised by one, which is a different claim and a more useful one.

Nearly every manufacturer raw is built on TIFF. ARW, NEF, ORF, RAF and the old CR2 all use its tag structure, which is why a program that understands one has a running start on the others. CR3, introduced with the EOS M50 in 2018, does not.

It is built on the ISO base media file format instead — the same nested-box design as MP4, MOV and HEIF. That is a genuine break rather than a version bump, and it is why CR3 support did not simply follow from existing code. Software had to learn a new container to read a file from a company it had supported for fifteen years.

CR3 brought a second option alongside the standard file: C-RAW, roughly 40 per cent smaller. It is not lossless. It discards data using a scheme related to how JPEG works, applied to sensor readings rather than to a finished image.

Most photographers who enable it do not realise this, because the menu calls it compressed rather than lossy and the results look fine. In ordinary use they are fine — the difference appears when a file is pushed hard, in heavy shadow recovery and in extreme crops, exactly where the latitude of raw is the reason for shooting it. The decision cannot be revisited afterwards, so it is worth making deliberately rather than for card space.

Because the container was new and undocumented, reading CR3 had to be worked out from scratch. Adobe added support reasonably quickly under commercial pressure; the open-source side took considerably longer, and for a period in 2018 and 2019 a new Canon body produced files that a great deal of software simply could not open.

That has largely resolved and it left a residue: older versions of otherwise capable programs still refuse CR3 while handling CR2 from the same manufacturer without difficulty. If a Canon file will not open in something that has always worked, checking which of the two formats it is comes before assuming damage.

Canon adopted the same underlying container that HEIF uses, and the same cameras that write CR3 often offer HEIF as a JPEG alternative. Both decisions come from the same place: the ISO base media format was the modern, well-understood way to build a media container in 2018.

One practical consequence is that a CR3 can hold a full HEIF preview rather than only a JPEG one, which is how ten-bit previews became possible. It also means the format has room for image sequences and multiple related images that nothing currently uses.

Some Canon bodies can record both halves of each dual-pixel photosite, roughly doubling the file size. The two views are separated by a fraction of a millimetre, which yields a very slight parallax between them.

What that buys is small and specific: a minor adjustment to the apparent focus plane, a small shift in bokeh, and some control over ghosting. It is not focus correction and will not rescue a missed shot. Canon’s own software is the only place the adjustments are available, so a dual-pixel CR3 converted elsewhere is simply a large ordinary raw.

CR3 arrived with the EOS M50 in 2018 and is what the R-series mirrorless bodies, the newer M-series and the recent DSLRs produce. CR2 is what everything before that wrote, which is a very large installed base — every Canon DSLR from 2004 to 2018.

So a Canon photographer with a decade of archives usually holds both, and they behave differently in older software. Sorting a mixed archive by extension before batch-converting avoids discovering the difference halfway through.

Camera model and serial number, lens including its serial on recent bodies, focal length, aperture, shutter speed, ISO, the exact date and time, the picture style, and whether C-RAW was used. Location where the camera was paired with a phone or has a receiver.

Little of this survives conversion to JPG or PNG in the way people assume — exposure fields usually carry across, location may or may not depending on the tool. For a photograph being published, that deserves a decision rather than a hopeful assumption.

To share or print, JPG at high quality. For further work outside a raw editor, or where every pixel must survive, PNG or TIFF. Canon’s own Digital Photo Professional applies the picture style and lens corrections the camera intended, which other converters approximate rather than reproduce.

Keep the CR3. The converted file has the white balance, the tone curve and the colour interpretation baked in permanently. And if the file is C-RAW, the original is already the reduced version — converting it further compounds a loss that was taken at the shutter press.