"It May Be Damaged or Use a File Format That Preview Doesn't Recognize"

You open an image on your Mac and get: “The file could not be opened. It may be damaged or use a file format that Preview doesn’t recognize.” That wording is unhelpfully broad. It covers a genuinely corrupt file and a perfectly good file in a format this version of macOS can’t decode, and it gives you no way to tell them apart. In practice the second case is far more common, and it has a quick fix.

The thirty-second test

Before changing anything, work out which problem you actually have. Drag the file into a Safari or Chrome window.

• It displays in the browser. The file is fine. Browsers ship their own image decoders, independent of Preview’s, and they’re often newer. You have a format-support problem, and converting solves it.
• It fails in the browser too. Now damage is likely, and the section at the end of this guide applies.

This one test saves most people from pointlessly reinstalling macOS over a file that was never broken.

What actually triggers it

HEIC from a recent iPhone on an older macOS

This is the big one, and it’s more specific than “old Mac can’t do HEIC.” macOS High Sierra introduced HEIC support back in 2017, so Preview will happily open plenty of HEIC files. The failures cluster around newer variants of the format.

Recent iPhones increasingly record 10-bit HEIC rather than 8-bit, and they embed colour-profile data that older decoders mishandle. The result is maddening: some HEIC photos open and others don’t, on the same Mac, from the same phone. People reasonably conclude the failing files are corrupt. They aren’t — they’re just a flavour of HEIC that this macOS version doesn’t fully implement. It’s a documented problem on Apple’s own discussion forums.

AVIF, and other formats newer than your macOS

AVIF support came to macOS relatively recently (Ventura onward in practice). On Monterey or earlier, an AVIF file produces exactly this error. The same logic applies to any format that postdates your OS: Preview can only decode what shipped with it, and Preview doesn’t gain new format support through app updates the way a browser does.

Camera RAW from a camera newer than your macOS

RAW is not one format but hundreds of camera-specific ones. Apple adds support for new camera models through macOS updates, so a RAW file from a body released after your OS will fail even though RAW “works” on your Mac. Updating macOS often fixes this specific case outright.

A file whose extension lies

Sometimes the extension doesn’t match the contents — a HEIC renamed to .jpg, or a WebP a website served as .png. Preview trusts the data over the name, finds something unexpected, and reports a format it doesn’t recognise. You can check with Terminal:

file ~/Desktop/your-photo.jpg

That prints what the file genuinely is. If it says HEIF or WebP while the extension claims JPEG, you’ve found your mismatch.

Open it now

Whatever the specific cause, converting to JPG or PNG sidesteps it, because those are formats every version of macOS has decoded for decades. This runs in your browser — nothing is uploaded, and it works on any Mac regardless of how old the OS is.

Note what this does and doesn’t mean: the converter reads the file with your browser’s decoders, which are newer and more complete than Preview’s. That’s exactly why it can open a file Preview refuses. If you want a lossless result instead of JPG, use the HEIC to PNG converter.

Other things worth trying first

If you’d rather keep the original format, these sometimes work:

• Open it in Photos instead of Preview. The two apps don’t share the same code path, and Photos occasionally succeeds where Preview fails.
• Update macOS. Most of the causes above are “this OS predates this format.” An update is the direct fix — assuming your hardware still receives them.
• Quick Look it. Select the file and press space. Quick Look sometimes renders a thumbnail from an embedded preview even when full decoding fails, which at least confirms there’s a real image in there.
• Re-download it. If it arrived over the web or a messaging app, an interrupted transfer produces a truncated file that genuinely is damaged.

One thing we’d steer you away from: the advice circulating about reinstalling macOS or creating a new administrator account to fix this. That’s a reasonable step for a Preview that crashes on every file, which is a different symptom. For a single file that other apps can open, it’s a lot of upheaval for nothing.

If the file genuinely is damaged

When the browser test also fails, the data itself is incomplete, and it’s worth being straight about the limits here: no converter and no repair tool can reconstruct image data that was never written. What you can do is go back to the source — ask the sender to resend it, re-export it from the original app, or pull it from a backup or from iCloud, where a complete copy may still exist. If it was recovered from a failing drive, a partial file is often the best that exists.

Frequently asked questions

Why do some HEIC photos open and others don’t?

Because HEIC isn’t a single thing. Bit depth (8-bit versus 10-bit), the colour profile, and which iPhone and iOS version produced it all vary, and older decoders handle some combinations and not others. Inconsistency is the signature of a codec gap, not of damage.

Does converting change the original file?

No. You get a new file; the original stays exactly as it was on disk. Nothing is overwritten.

Will the converted photo keep its date and location?

Metadata is stripped by default, which includes the capture date and any GPS coordinates. That’s the safer default for a file you might share. Keep the original if you need that information preserved.

Can I convert a whole folder at once?

Yes — drop in as many files as you like and download the results as a single ZIP. Because the work happens on your own machine, large batches are limited by your Mac, not by an upload queue.

Is Preview’s own Export option a fix?

Only if Preview can open the file in the first place, which by definition it can’t here. File → Export is genuinely useful for converting formats Preview does read, so it’s worth remembering for other situations.