How to blur part of a screenshot on Mac

macOS can’t blur part of an image: Preview and the screenshot thumbnail have no blur tool. In Preview you can cover the part with a filled shape instead; to really blur or pixelate a region, use an editor that has the tool, such as SimpleShot, where it takes one drag. For passwords, card numbers and other secrets, a solid box is safer than any blur.

Updated November 2, 2026

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Hide part of a screenshot in Preview

Open the screenshot in Preview and click the Markup button (the pen tip) to show the toolbar.
Click Shapes and choose the rectangle. Draw it over the part to hide.
Pick a fill colour in Fill Color (and the same Border Color), so the box is solid.
Choose File › Export and save a copy. Share the exported file.

It hides, but doesn’t blur: you get a coloured box. Some people search for a blur in Photos too: it doesn’t have one for part of a picture either.

Blur part of a screenshot with SimpleShot

Take the screenshot with ⇧⌘4, or open an image in SimpleShot.
Press B for Blur (or X for Pixelate) and drag over the area. Set how strong it is on the right.
Copy, save or drag the result into a message. Undo works step by step if you blurred too much.

SimpleShot is a free capture app for Mac. The same editor has arrows, text, numbered steps, a highlighter and spotlights, so you blur the noise and point at what matters in one go.

Blur, pixelate or a solid box?

	Blur	Pixelate	Solid box (Secure Redact)
Looks	Soft, natural	Blocky	A plain colour block
Good for	Busy backgrounds, faces in a crowd, notifications	Names, avatars	Passwords, card and phone numbers, e-mails, keys
Can it be read back?	Short text sometimes can, if the blur is weak	Short text sometimes can	No: the covered pixels are replaced in the file

That is why SimpleShot has Secure Redact (press D) beside Blur: it replaces the covered pixels with solid colour in everything you export, copy or share. Hide Sensitive Data goes further: it reads the capture on your Mac, counts the e-mail addresses, phone and card numbers, IBANs and keys still showing, and covers them all in one click. More in how to redact a screenshot on Mac.

Questions

Can you blur part of a picture in Preview on a Mac?

No, Preview has no blur tool. Cover the part with a rectangle filled with a colour, or use an editor with a blur tool.

How do I blur a screenshot on a Mac for free?

Open it in SimpleShot, press B and drag over the area. It is free, with no watermark and no account, and works on screenshots and on any image you open.

Is blurring enough to hide a password or a card number?

Not always: a light blur or pixelation of short text can sometimes be read back. Use a solid box for secrets, and share an exported copy rather than an editable file.

Can I blur a screenshot without installing anything?

Yes, in the browser: redact a screenshot online covers areas with solid pixels and hide personal info finds e-mails, numbers and keys for you. The image is read in the tab and never uploaded.

Blur the noise.
Box the secrets.