Convert HEIC to JPG on Mac and Set iPhone to JPEG

Open the HEIC file in Preview and choose File > Export. Select JPEG in the Format menu, choose the quality, then save with a new name or in a different folder. If the format you need is hidden, hold Option while opening the Format menu. Keep the HEIC original until you have opened the JPEG and confirmed it works in the receiving app or website.

Open the images in one Preview window, select the images in its sidebar, and follow the same export steps. Save the results in a separate folder so you can distinguish originals from exports. Inspect a few results before converting a large collection. If your goal is one rejected upload, start with that photo rather than replacing the entire library.

On a supported iPhone, open Settings > Camera > Formats and select Most Compatible. New photos use JPEG; High Efficiency uses the more space-efficient HEIF format. This setting affects new captures, so a photo taken earlier can still be HEIC. Sharing by email or AirDrop may convert an image when needed, but Apple describes that as conditional; explicit export is clearer when a website requires JPEG.

Use the exported JPEG, not the similarly named original. Open it and check the photo’s orientation and any small text you need to preserve. If the website has a file-size limit, check that separately: choosing JPEG does not guarantee a particular size. Avoid changing only the filename from .heic to .jpg, because that leaves the actual image format unchanged.