You took a photo on your iPhone, sent it to someone, and they replied saying they can't open it. Or you tried uploading it to a website and got an error you weren't expecting. The file has a .heic extension and suddenly nothing wants to cooperate with it. This is a very common situation, and it has a simple fix once you understand what's going on.
What HEIC actually is
HEIC stands for High Efficiency Image Container. Apple switched to it as the default photo format starting with iOS 11 in 2017. The reason is straightforward: HEIC files are roughly half the size of JPEGs at comparable visual quality. For a phone with 64 or 128 GB of storage and a 48-megapixel camera, that matters.
The format also supports 12-bit color depth compared to JPEG's 8-bit, which means more color information is captured per shot. It can store Live Photo data, Portrait mode depth maps, and non-destructive edits alongside the original image in a single file. When you adjust brightness in the Photos app, your original is still preserved inside that HEIC container.
So no, HEIC is not a bad format. Apple didn't make it annoying on purpose. The problem is compatibility, not the format itself.
Why it breaks everywhere else
HEIC is built on HEVC compression, the same codec used for video streaming on Netflix and YouTube. That compression is licensed, which means software developers have to pay to implement it or go through a non-trivial integration process. A lot of platforms and apps simply haven't bothered.
Windows doesn't open HEIC natively unless you install a codec from the Microsoft Store. Google Docs, most image editing tools, website upload forms, email clients on non-Apple systems, many design tools... they all either reject HEIC files outright or display nothing. macOS handles HEIC fine because Apple controls both the format and the operating system. Outside the Apple ecosystem, you're on your own.
This isn't going to change dramatically anytime soon. JPG has been around since 1992, is supported by every device on the planet, and will continue to be the safe choice for sharing and uploading for the foreseeable future.
How to convert HEIC to JPG
If you want to stop the problem at the source, go to Settings on your iPhone, then Camera, then Formats. Switch from "High Efficiency" to "Most Compatible." Your phone will now shoot in JPG by default. You'll lose about half your storage efficiency per photo, but you'll never deal with this compatibility issue again. For most people, that's the right tradeoff.
This only affects new photos. Your existing HEIC library stays as-is.
For sharing individual photos from your phone, iOS does something useful: when you share a photo to a non-Apple destination via Mail or Messages, it often converts automatically to JPG on the way out. If you need to force it, open the photo, tap Share, and choose "Save to Files." That export step triggers a JPG conversion. Not elegant, but it works for one or two photos.
On a Mac, open the HEIC file in Preview, go to File, then Export, and pick JPG from the format dropdown. For multiple files, select them all in Finder and do the same. macOS handles this natively with no extra software. If you have a large library to convert, select all the files in Finder, right-click, go to Quick Actions, and choose "Convert Image." It converts them all in place.
On Windows, your options depend on what's already installed. You can get HEIC support by installing the HEIF Image Extensions from the Microsoft Store (free), which adds native HEIC viewing to Windows. For actual conversion, either use an online tool or a free desktop app like XnConvert, which handles bulk conversion well.
For files already on your computer, especially on Windows where native support is still unreliable, an online converter is often the simplest route. You drop the file in, get a JPG back, and you're done. No installation, no account required.
What you lose in the conversion
JPG is a lossy format. When you convert from HEIC to JPG, some data is permanently discarded. At high quality settings (90% or above), the visual difference is not visible in normal use. You'd have to zoom in significantly and compare side by side to notice anything.
What can't come back: the 12-bit color depth gets downsampled to 8-bit, any edits made in the Photos app get baked into the exported file rather than staying non-destructive, and Live Photo data and Portrait mode depth maps are stripped out entirely.
For everyday sharing, uploads, or sending to colleagues, none of that matters. Where it matters is archiving. If you want to preserve your photos at full original quality long-term, keep the HEIC files as your master copies and convert to JPG only when you need to share or upload. That way you have both.
One thing worth knowing about batch conversion
If you're sitting on a folder with hundreds of HEIC files, converting them one by one is impractical. On Mac, the Quick Actions method in Finder handles large batches well. On Windows, XnConvert is free and can process entire folders at once with the output settings you specify. Online tools are better suited for single files or small batches, not large libraries.
The simplest long-term answer is switching your camera format to JPG going forward and converting the existing backlog once, rather than dealing with this repeatedly.