What is HEIC?
High Efficiency Image File Format (HEIC)
HEIC is format used by default on photos on iOS 11 and higher for iPhone and iPad,
The format was designed and implemented to save storage space on your device but keeping the high-quality photos you expect from your iPhone. But with a big change like this you can expect a few compatibility issues that can cause issues viewing photos outside of Apple Products.
The Images are automatically converted when uploading to social media like Facebook, Instagram, Twitter.
iOS 11 does have an inbuilt tool to automatically transfer photos and videos in a compatible format for Mac or PC users. Which you would expect should be as simple as plugging into a Windows machine but in most cases does not work as expected.
You can turn off the HEIC setting from your device so that it will automatically take photos in JPEG Format by following the steps below
Settings > Camera > Formats > Most Compatible
There is also a very simple and free tool that I recommend using if you ever get to the stage of having photos stuck in the HEIC format that you need to convert.
It a great free and easy to use website which allows you to convert up to 50 photos at one time and download it as a folder with all the photos converted in JPEG.