When you take a photograph with a modern iPhone, it defaults to saving the image in the highly efficient HEIC format. While HEIC saves space on your phone, it is notoriously incompatible with older Windows PCs, web upload forms, and specific graphic design software. If you attempt to email an HEIC file, the recipient might not be able to open it. You do not need to download sketchy third-party conversion software to fix this. The native macOS Preview application contains a massive, hidden format-conversion engine that can instantly translate images between JPEG, PNG, HEIC, TIFF, and PDF.
Accessing the Export Engine
You cannot simply rename the file extension from .heic to .jpg in the Finder. This breaks the file structure. You must force the Quartz engine to mathematically re-render the pixels into the new format.
- Double-click the target image to open it in Preview.
- Look at the main menu bar at the absolute top of your Mac screen. Click File.
- Select Export from the drop-down menu. (Do not click Save).
A standard dialogue box will appear, allowing you to rename the file and choose where to save the new copy.
Choosing the New File Format
At the bottom of the Export dialogue box, you will see a drop-down menu labeled Format.
- Click the Format menu.
- By default, it will list standard options: HEIC, JPEG, JPEG-2000, OpenEXR, PDF, PNG, and TIFF. Select the universally compatible JPEG.
Pro Tip: If you need a highly obscure, legacy file format (like a Microsoft BMP or an ancient GIF), hold down the Option key on your keyboard while clicking the Format drop-down menu. The list will instantly expand to reveal hidden, legacy export options.
Adjusting Quality and File Size
When you select JPEG or HEIC, a new Quality slider will appear below the format menu.
This slider directly controls the compression algorithm. If the website you are uploading to has a strict 2-Megabyte file size limit, simply drag the slider slightly to the left (toward “Least”). Preview will dynamically calculate the math in real-time, displaying the projected “File Size” directly below the slider, allowing you to perfectly compress the image to fit the requirement before you click Save.