How to blur sensitive information in a screenshot on a Mac

Blur is not always redaction

A light Gaussian blur over text in a known font can sometimes be reconstructed, because the blur is a predictable transform. Coarse pixelation destroys more information, and an opaque shape destroys all of it. For anything that matters, such as keys, tokens, or account numbers, use coarse pixelation or a solid box, and crop it out entirely when you can.

Method 1: Markup in Preview or the ⌘⇧5 thumbnail

1. Take the screenshot, then click the floating thumbnail, or open the file in Preview and click the Markup toolbar button.
2. Choose Shapes, pick the rectangle, and drag it over the sensitive area.
3. Set the fill color to a solid color and make sure the shape is fully opaque.
4. Save. Check the result at full size before sharing.

Note. Markup has no blur or pixelate tool. An opaque rectangle is the only safe option, and a semi-transparent one is not safe at all.

Method 2: Blur or pixelate in the Shotnix editor

1. Take the capture and press ⌘E on the overlay to open the editor.
2. Choose Blur (B) or Pixelate (P) and drag over the area. Both cover what's under them right to the edges. Raise the strength slider for text; pixelate uses real mosaic blocks.
3. For absolute certainty, draw a filled rectangle over the area instead.
4. Press ⌘C to copy or ⌘S to save. The redaction is baked into the exported pixels.

Screenshot annotation in Shotnix →

Method 3: Redacting inside a screen recording

For video, the Shotnix editor has a Blur annotation (press B) that stays on the private detail through zooms. Set when it starts and ends with its bar on the timeline, and use it to cover a notification or a sidebar for part of a recording. It is a heavy blur, not an opaque box, so for keys and tokens, cut that part of the video or crop it out.

Video demo editor →

Checklist before you share

• Browser tabs: titles often contain names, ticket numbers, or document titles.
• The URL bar: query strings and IDs.
• Notifications and the menu bar: calendar events, message previews, account names.
• Autocomplete and recent items in dropdowns and search fields.
• Second monitor and background windows if you captured a whole display.
• Terminal history and environment variables in scrollback.

Questions