HEIC is a new image format, built to be more efficient than existing file types. It stands for High-Efficiency Image Container, and it’s a variation of HEIF (High-Efficiency Image File Format).

HEIC files are, on average, half the size of JPGs, while offering better quality. HEIF and HEIC are also found in macOS versions from High Sierra (OS X 10.13) right up to the current version of macOS

The easiest way to turn a HEIC file into a JPG file on a Mac is to use the built-in Preview app

1. Use the Preview app to open the HEIC image. You can open more than one HEIC file if you want  to bulk convert HEIC images to JPG

2. From the top menu, select File and then Export.

3. You will see a Format drop-down menu. Use it to select JPG as the format.
4. Give your new JPG photo a name and choose where you want to save it.
5. Click Save, and you're done.

NOTE

You can also use the Photos app on a Mac to convert HEIC files to JPG's.

Select the images you want to convert, and simply click and drag them into any Finder window. They’ll automatically be converted to JPGs. You can do this with single images, or you can convert multiple HEIC files to JPG at once.