Can I convert HEIC to JPEG directly on my iPhone?

Yes. If you have the iPhone set to “High Efficiency,” you can still share or export photos as JPEG. When you share a photo via email or messaging, the iPhone automatically sends a JPEG copy. For bulk conversion, you can use a third-party app on a computer after transferring the HEIC files.

Is it safe to rename a .heic file to .jpg?

No. Renaming only changes the file extension, not the internal data. The file remains HEIC and will not open as a JPEG. You must either install the HEIF Image Extensions on Windows or convert the file with a proper converter.

How can I tell if a photo is truly corrupted or just incompatible?

Check the file extension. If it is .heic, it is a compatibility issue. If it is .jpg but shows a grey lower part, garbled colors, or a file size much smaller than expected, it is likely corrupted. A repair tool may help recover the image.

iPhone Photos Won't Open on PC: HEIC vs JPEG Explained

Q: Why does Windows say “a device attached to the system is not functioning” when I plug in my iPhone?

This error often occurs when the iPhone’s transfer setting is on “Automatic” and the conversion process fails. Changing the setting to “Keep Originals” usually resolves it. Also try a different USB cable or port.

iPhone photos that refuse to open on a PC usually point to a format clash, not broken files. Apple phones capture images in HEIC (High Efficiency Image Format) or JPEG. Windows cannot read HEIC natively. Files appear blank, fail to copy, or throw the error “a device attached to the system is not functioning.” Here is how to control the HEIC-versus-JPEG choice on the iPhone, distinguish a format problem from real corruption, and recover photos that are genuinely damaged.

Why IPhone Photos Look Broken on Windows

Copy photos from an iPhone to a Windows machine and the usual culprit is HEIC. Windows lacks built-in support for the format. Without the right codec the operating system cannot decode the image. Thumbnails show a generic icon, the file appears as a tiny square, or an error message blocks you. This is not corruption. It is a compatibility gap.

An interrupted USB copy causes a different problem. If the connection drops mid-transfer the file gets truncated. A truncated JPEG often displays its top half correctly while the bottom half turns grey or white. That is real corruption, but it lives only in the copy process.

IPhone Settings That Control HEIC vs JPEG

Two settings on the iPhone decide whether your photos are HEIC or JPEG, and how they behave while copying.

Camera Format

Go to Settings > Camera > Formats. You get two choices:

High Efficiency saves photos as HEIC files. They use less storage but Windows does not support them natively.
Most Compatible saves photos as JPEG files. JPEG works everywhere, on Windows, macOS, and every other device.

Switch to “Most Compatible” and every new photo lands as a JPEG. No more format headaches.

Transfer to Mac or PC

Head to Settings > Photos > Transfer to Mac or PC. This governs what happens when you copy photos over a USB cable or a Wi-Fi connection:

Automatic tells the iPhone to convert HEIC files to JPEG during the copy. Convenient, but a failed conversion or a shaky connection can trigger errors.
Keep Originals copies the files exactly as they sit on the phone, no conversion. If “High Efficiency” is active you get .heic files. This setting is the go-to fix for the copy error “a device attached to the system is not functioning.”

The Copy Error “A Device Attached to the System is Not Functioning”

This error surfaces when you try to import photos from an iPhone to a Windows PC over USB. The phone’s copy mode clashes with Windows. Change Settings > Photos > Transfer to Mac or PC from “Automatic” to “Keep Originals.” The iPhone stops trying to convert files mid-copy. That alone often kills the error. Reconnect the phone and try the copy again.

If the message persists, swap the USB cable, try a different port, restart both devices, or sidestep the wire entirely with email or cloud storage.

How to Open HEIC Files on Windows

Keep the iPhone on “High Efficiency” and you can still open those HEIC files on a PC. Microsoft publishes a free add-on called HEIF Image Extensions in the Microsoft Store. Install it. File Explorer and the Photos app then display HEIC thumbnails and open the images normally. The add-on does not convert anything. It simply teaches Windows to read the format.

Do not rename a .heic file to .jpg. That changes the label, not the data inside. Windows still cannot decode it. Install the extensions or use a dedicated converter.

Real Corruption vs Format Incompatibility

A photo that looks broken is not always corrupted. Here is the split:

Format incompatibility: The file carries a .heic extension, or Windows shows a blank thumbnail and refuses to open it. File size looks normal. Fix: install HEIF Image Extensions or set the iPhone to “Most Compatible.”
Corrupted file: The image opens partway (top half visible, bottom half grey), the picture is scrambled with coloured streaks, or you get a “file is damaged” error. The file size may be smaller than expected. Interrupted USB copies and faulty storage cause this.

Suspect real corruption? Do not rename the file or try to edit it. Reach for a repair tool built for JPEGs. JPEG Repair attempts to pull readable image data out of truncated or damaged files.

Preventing Future Problems

Stop copy trouble before it starts:

Set Settings > Camera > Formats to “Most Compatible.” All new photos save as JPEG.
Set Settings > Photos > Transfer to Mac or PC to “Keep Originals” to dodge conversion errors.
Use a stable USB connection. Plug directly into the machine, not through a hub. Never yank the cable mid-copy.
After copying, open a few files on the PC and confirm they display correctly before you delete anything from the iPhone.

Already sitting on a phone full of HEIC files? Convert them in bulk. On a Mac use “Export Unchanged Original.” On Windows, install the HEIF Image Extensions first, then run a third-party converter.

What to Do If Your JPEG is Still Broken

You have confirmed the file is a JPEG, not HEIC, and it still shows corruption: a grey lower portion, random noise, a “file cannot be opened” error. The data is likely truncated. An interrupted USB copy does this. A dedicated repair tool can sometimes recover the image. JPEG Repair is a free online service that attempts to fix corrupted JPEGs. No watermark. No app install. You upload the file and the service processes it.