I take a lot of screenshots. Bug reports, tutorials, documentation, Slack threads — it adds up fast. And at least once a week, I catch myself about to share something with my email, an API key, or a client's name sitting right there in the image.
macOS doesn't make redaction obvious. So I tested every method I could find. Here's what actually works.
The Problem
Screenshots contain more than you think:
- Email addresses, phone numbers
- API keys, passwords, internal URLs
- Other people's names and data
- Browser tabs with sensitive info
Before sharing anything, scan the whole image. It takes 10 seconds.
Method 1: ScreenSnap Pro (My Go-To)
If you take screenshots regularly, a dedicated tool saves serious time. ScreenSnap Pro has blur and pixelate built into the capture workflow:
- Capture your screenshot
- Click Blur or Pixelate in the annotation bar
- Adjust intensity
- Draw over the sensitive area
- Done — image is flattened (no recoverable layers)
The key advantage: redaction happens during capture, not as a separate editing step.
Method 2: Preview with Shapes (Free, Built-in)
Preview doesn't have a blur tool (surprisingly). But you can cover areas with shapes:
- Open screenshot in Preview
- Click Markup toolbar (pencil icon)
- Add a rectangle shape
- Set fill to solid color, border to none
- Position over sensitive area
- Save
Limitation: Shapes can potentially be moved if someone opens the file in Preview. Not ideal for truly sensitive data.
Method 3: Photos App Retouch (Hidden Gem)
The Photos app has a Retouch tool that smudges content. Not a clean blur, but it works for small text:
- Import screenshot into Photos
- Edit → Retouch tool
- Paint over sensitive info
- Export back to Finder
Best for quick, informal redactions. Looks messy on larger areas.
Method 4: Skitch (Free)
Skitch by Evernote has a proper pixelate tool:
- Download from Mac App Store
- Drag screenshot in
- Click Pixelate
- Draw over area
- Export
Simple, free, does the job. No blur option though (pixelate only).
Method 5: iPhone Markup (Workaround)
If you have an iPhone, AirDrop the screenshot over and use iOS Markup. It's actually faster than Preview for quick redactions.
Blur vs. Pixelate: When to Use Each
| Use Case | Method | Why |
|---|---|---|
| Text (emails, passwords) | Blur | Softer, professional look |
| Faces | Pixelate | Industry standard |
| Large areas | Solid cover | Cleaner result |
| Numbers | Either | Personal preference |
The Mistakes That'll Get You
These are the ones I see constantly:
Semi-transparent shapes — If someone adjusts levels in Photoshop, they can recover the text. Always use 100% opacity.
Not flattening layers — Some editors save blur as a separate layer. Always flatten before sharing.
Weak blur intensity — If you can vaguely read it, so can others. When in doubt, blur more.
Forgetting window titles and tabs — Sensitive data hides in browser tabs, file paths, notification badges, menu bars.
Leaving metadata — Screenshots contain location, device info, timestamps. Strip metadata for sensitive shares.
The Surprising Security Finding
AI tools are getting better at reversing weak pixelation. Short text strings with small pixel blocks are increasingly recoverable. For truly sensitive data (passwords, API keys), solid rectangles flattened into the image are the safest method. Blur is second. Pixelation is third.
TL;DR
- Occasional edits: Preview shapes or Skitch
- Regular screenshot work: ScreenSnap Pro (blur/pixelate built into capture)
- Most secure: Solid shapes, flattened, saved as PNG/JPG
- Always: Zoom in to verify, check the whole image, save as new file
Originally published on ScreenSnap Pro
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