If you've ever received photos from an iPhone and wondered why Windows can't open them, you've met HEIC. Apple adopted the format in 2017 because it produces smaller files at higher quality than JPG. Windows didn't get the memo.
The simplest fix is installing the free HEIF Image Extensions from the Microsoft Store. Once installed, HEIC files open normally in Photos, Paint, and File Explorer thumbnails. Search "HEIF" in the Store, install it, and you're done. If the free extension doesn't work (some older Windows 10 builds require a paid HEVC codec), you can install the HEVC Video Extensions for about $1.
Alternatively, you can convert HEIC to JPG before opening. Tools like fwip handle this instantly in your browser — drop the file, get a JPG back, no upload required. This is the best option when you need to share the photo with someone who also doesn't have HEIC support.
For bulk conversion, IrfanView (free) and Adobe Lightroom both handle HEIC natively. If you just need to view one photo quickly, Google Photos in any browser will display HEIC files without any software installation.