How to hide sensitive text in a Mac screenshot
Cover the text with a solid, opaque block, then share the image you saved after covering it. Blur and pixelate keep traces of the words, so a solid block is the safer choice.
What macOS does on its own
Apple's list of Markup tools for images has no blur or pixelate tool, and a filled shape does the job.
- Open the screenshot in Preview and show the Markup toolbar.
- Click Shapes, choose a rectangle and drag it over the text.
- Use Fill Color to fill the shape with a solid color.
- Save the image.
Apple says you can't edit, move or delete annotations on an image file after you save it, so check the cover first.
Why solid is safer than blur
Pixelate averages the pixels in each block and blur smears them together, so both are still made from the original letters. A peer-reviewed 2016 study recovered text from both, including real-world examples, and concluded that neither is a viable way to redact text. Its method needs the typeface and font size, so not every blur can be read. For anything that matters, assume it can.
A solid block keeps nothing of what it covers. It does show how long the hidden text is, so make it wider than the words when the length could give them away.
Hide text in Shotbolt
- Open the capture in the editor: double-click its Quick Access card, or open it from History. For a picture file, choose Tools → Annotate Image File…
- Press P for Pixelate / Blur.
- In the inspector, under Effect, choose Solid, an opaque black block. The editor remembers the effect you used last.
- Drag over the text. The box grows to take in words it overlaps. Or press Tab to step through the lines of text and Return to cover one.
- Zoom in and check the edges.
- Press Command-S to save, or Command-Return for Done, which saves, copies and closes.
To match the background, press O for Patch and cover the text with a copy of a clean area, at full opacity and untilted. If the private part sits at an edge, crop it away with K.
Redact Pro (Shotbolt Pro) finds the text for you. Press X and Shotbolt reads the screenshot on your Mac and lists what it found by type, such as email addresses, card numbers and API keys, with Solid as its default cover. It checks only the types switched on in Settings → Privacy and only text it can read, so it can miss words, and a face or a QR code stays visible. Check the result before you share it. More in Help.
Which file is safe to share
After Save or Done, the capture's file is a flat picture with the covers in its pixels. It holds no layers and no hidden copy of the original. The same goes for Save As, Copy, Drag and Share… in the editor.
These can still show the text:
- A saved file after Copy. By default, every screenshot is saved the moment you take it. Copy (Shift-Command-C) puts the covered picture on the clipboard and leaves that file as it was. Its message offers Save Edit, which writes the cover into the file.
- The clipboard before you finish. A new screenshot is copied by default too. Save, Copy and Done replace it.
- The file you started from. Save As leaves the capture's own file unchanged, and Annotate Image File… only reads the picture you opened.
- A hidden or see-through cover. A hidden layer is left out of the picture, and a cover below full opacity lets the text show. Check Layers.
What stays on your Mac
To keep marks editable, Shotbolt stores the original pixels and your layers with the capture in History, on your Mac. That is why a cover can be removed later, and why History search can still find words under one. None of this goes into the finished picture. A deleted capture stays in Recently Deleted for up to 30 days unless you empty it.
Questions
Can someone remove a solid cover from an image I shared?
No. The cover is part of the pixels, and what was under it is not in that file. A picture that was already a JPEG can hold faint traces around the block, so make it generous.