How to Convert Image Formats Using the Preview App on macOS

When you download a high-resolution photograph from your iPhone to your Mac, it is often saved in Apple’s proprietary HEIC format. While HEIC saves a massive amount of storage space, many older websites, government portals, and third-party applications simply refuse to upload or open the file, demanding a standard JPEG instead. You do not need to download third-party conversion software from the App Store; the native macOS Preview application includes a powerful, built-in image conversion engine that can instantly transcode files between JPEG, PNG, HEIC, and even PDF formats.

How to Convert a Single Image

The conversion tool is located within Preview’s standard export menu.

1. Double-click the image (e.g., your .heic file) to open it in Preview.
2. In the top menu bar (next to the Apple logo), click File.
3. Select Export… from the drop-down list. (Do not click “Export as PDF”; click the standard “Export…” option).
4. A new save dialog box will appear. Look at the bottom of this window for the Format drop-down menu.
5. Click the Format menu and change it from HEIC to JPEG.
6. A new Quality slider will instantly appear. Dragging the slider toward “Best” will preserve maximum image quality but result in a larger file size.
7. Choose where you want to save the new image (e.g., your Desktop) and click Save.

macOS will instantly generate a brand-new, universally compatible JPEG file on your Desktop, leaving the original HEIC file completely untouched.

Unlocking Hidden Image Formats

By default, the Format drop-down menu in Preview only shows the most common file types: JPEG, JPEG-2000, OpenEXR, PDF, PNG, and TIFF. However, Preview’s underlying rendering engine supports significantly more formats.

If you need to export an image into a legacy or highly specialized format (like a GIF, a Microsoft BMP, or an older Photoshop PSD file), you must use a hidden modifier key.

When you are in the Export dialog box, hold down the Option (⌥) key on your keyboard, and then click the Format drop-down menu. The list will instantly expand, revealing several advanced, hidden file types that are normally suppressed by the operating system to prevent clutter.

How to Convert Multiple Images Simultaneously

If you need to convert 50 HEIC photos into JPEGs, converting them one by one is tedious. You can batch-convert them all at once.

1. Highlight all 50 images in your Finder window, right-click, and select Open With > Preview.
2. In Preview, click inside the left-hand thumbnail sidebar and press Command + A to select all 50 thumbnails.
3. Click File > Export Selected Images…
4. A window will appear asking you to choose a destination folder. Look at the bottom left corner and click the Options button.
5. Change the Format to JPEG and click Choose.

Preview will instantly transcode all 50 images simultaneously and dump the new JPEGs into your selected folder.