How to Add a Transparent Text Watermark to Images Using Preview on macOS

When you share an original photograph, a digital illustration, or a confidential PDF document online, you risk having your work stolen or forwarded without permission. To protect your intellectual property, you should always apply a watermark. You do not need to buy an expensive Adobe Photoshop subscription to do this; you can create a custom, semi-transparent text watermark directly within the macOS Preview application in just a few clicks.

How to Create the Watermark Text

Because Preview is a native Apple application, you can use its advanced Markup tools to overlay vector text onto any image (JPEG, PNG, HEIC) or PDF file.

1. Double-click your image or PDF to open it in Preview.
2. Click the Markup Toolbar icon in the top right corner (it looks like a small pencil tip inside a circle).
3. In the new toolbar that appears, click the Text icon (a small square with a capital ‘T’ inside).
4. A small text box will drop into the center of your image. Double-click the word “Text” inside the box and type your watermark (e.g., “CONFIDENTIAL” or “© Jane Doe 2024”).

How to Style and Position the Watermark

A good watermark should be highly visible but not completely obscure the image underneath it.

1. Click the edge of the text box to select it.
2. Click the Text Style icon (the italic A) in the Markup toolbar.
3. Change the font to something thick and bold, like Impact or Arial Black.
4. Increase the font size significantly (e.g., 64pt or larger) so the text stretches across a large portion of the image.
5. Change the font color to a solid White or light Grey, which typically contrasts well against most photographs.
6. Click and drag the text box to the center of the image. You can also hover your mouse just outside one of the corner handles and drag to rotate the text diagonally across the screen.

How to Apply Transparency (Opacity)

A solid white block of text ruins the photograph. To make it a true watermark, you must make the text semi-transparent so the underlying image bleeds through.

1. Ensure your text box is selected.
2. Click the Text Style icon again to open the font menu.
3. Click the colored square located on the right side of the font menu to open the macOS Colors Palette window.
4. At the very bottom of the Colors window, you will see a slider labeled Opacity.
5. Drag the Opacity slider down to about 30% or 40%.

The text on your image will instantly become ghostly and transparent. Your photograph is now protected. Press Command + S to permanently flatten the vector text into the image and save the file.