How to Open HEIC Files on Windows (Without Installing Anything)
You sent photos from your iPhone to a Windows PC and they will not open. Here are the options, fastest first.
Option 1: Convert to JPG in your browser
The quickest fix needs no installation. Open an online HEIC to JPG converter that runs in your browser, add the files and download the JPGs. Choose one that does not upload your files, since the photos may contain personal data.
Option 2: Install the Windows codecs
Windows can open HEIC if the HEIF Image Extensions and HEVC Video Extensions are installed from the Microsoft Store. The HEVC extension may cost a small fee on some versions of Windows. After installing, the Photos app and File Explorer thumbnails should work.
This lets you view the files, but programs that do not use the Windows codecs, as well as websites, will still reject them.
Option 3: Stop creating HEIC
On the iPhone go to Settings, Camera, Formats and choose Most Compatible. New photos will then be JPG. When you transfer by cable, Photos settings also have a Transfer to Mac or PC option: choose Automatic and iOS converts to JPG on the fly where needed.
Which should you pick?
For a one-off batch, convert in the browser. If you work with iPhone photos on Windows all the time, switch the camera to Most Compatible or install the extensions.