This article explains how to convert a HEIC image to JPEG format on a Mac using either the Preview application that comes with your Mac or the Squoosh website in a browser.
How to Convert HEIC to JPG on Mac
Converting HEIC to JPEG is easy when you use the Preview application that comes with every Mac. It only takes a few steps to convert your image file to a more recognizable format.
Find the file you want to convert and double-click it to open Preview. You can also drag and drop an image onto the Preview icon in the Dock.
In Preview, click File > Export.