When you are building a presentation or designing a flyer on your Mac, you often need to insert an image (like a company logo or a product photo) without the ugly white box surrounding it. Instead of buying expensive professional photo editing software like Adobe Photoshop just to perform this one simple task, you can use the built-in macOS Preview app. Preview contains a hidden “Instant Alpha” tool that allows you to easily strip away solid background colors and save the image with a transparent background.
Preparing Your Image
Before you begin, you must ensure your image format supports transparency. JPEGs (.jpg) mathematically cannot hold transparent data; if you try to make a JPEG transparent, the background will simply turn solid white. Your file must be a PNG (.png) or a GIF.
If your current image is a JPEG, you can easily convert it using Preview.
- Double-click your image to open it in Preview.
- Click File in the top menu bar, then select Export.
- In the Format drop-down menu, choose PNG. Make sure the “Alpha” checkbox is checked, and click Save.
- Open your newly created PNG file in Preview.
How to Use the Instant Alpha Tool
The background removal tool is hidden inside the advanced markup menu.
- With your PNG open in Preview, look at the top right corner of the application window.
- Click the Markup Toolbar icon (it looks like a small pencil tip inside a circle). A new horizontal toolbar will appear directly below the main menu.
- On the far left side of this new toolbar, click the Instant Alpha tool. The icon looks like a magic wand with small stars around it.
- Your mouse cursor will change to a crosshair. Move this crosshair directly over the background color you want to remove (e.g., the white space around a logo).
- Click and hold your mouse button down, and slowly drag your mouse slightly to the right.
Refining the Selection
As you drag your mouse, a red mask will begin to spread across the background. This red overlay indicates exactly which pixels Preview is about to delete.
If you drag your mouse too far, the red mask will bleed into your actual logo, meaning you will accidentally delete parts of the image you wanted to keep. If this happens, simply drag your mouse backward (to the left) to reduce the sensitivity until only the background is highlighted in red.
Once the selection is perfect, release your mouse button. The red mask will turn into a moving dotted line (often called “marching ants”). Finally, press the Delete key on your keyboard. The solid background will vanish, replaced by a grey-and-white checkerboard pattern, which is the universal design symbol for complete transparency. Press Command + S to save your beautiful, newly transparent PNG.