Selective Blur Brush — Free Online Mask-Based Blur Tool
Sometimes you don't want to blur the whole image — just the busy background, the face of a stranger in your shot, or the address on a piece of mail. Selective Blur is the precise tool for that. Paint a mask exactly where you want softness, refine with the eraser, and export a result that looks like it came from a $2,000 lens or a privacy-trained editor. No subscription, no upload — pure browser canvas processing.
What is the Selective Blur Brush — Mask-Based Blur?
A mask-based blur tool that lets you paint blur intensity onto specific regions of an image while keeping the rest perfectly sharp. The blur radius and brush size are independently adjustable.
Key features
- Brush-painted mask for pixel-precise blur control
- Adjustable blur radius from 1 px (subtle) to 50 px (full anonymization)
- Adjustable brush size from 10 px to 250 px
- Eraser mode to refine or remove blur regions
- Soft, feathered brush edges for natural transitions
- Live preview cursor showing brush footprint
- Original-resolution export — no downsampling
- 100% in-browser — completely private, no uploads
How it works
The tool maintains three layers internally: the sharp original, a fully-blurred copy (using CSS `filter: blur(N)`), and a grayscale mask. Where the mask is white, the blurred layer is composited over the sharp original. Where the mask is black, only the sharp original shows. Brushing paints white into the mask with a soft radial gradient, while the eraser paints black — this creates seamless feathered transitions.
Why use this tool
Most blur tools force you to blur everything. Selective Blur gives you Photoshop-level mask control in seconds — no layers, no Quick Mask, no learning curve. It's also vastly more private than uploading sensitive screenshots to cloud-based redaction tools.
Common use cases
- Anonymizing faces in shared photos
- Redacting license plates, addresses, screen contents
- Creating fake depth-of-field (bokeh) portrait effects
- Hiding distracting elements in landscape or street photography
- Protecting private information in screenshots before posting
- Softening busy backgrounds in product photos
- Drawing attention to a subject by blurring its surroundings
How to use this tool
- Upload Your Photo — Choose any JPG, PNG, or WEBP image where you'd like to blur only specific areas — backgrounds, faces, license plates, or distractions.
- Set Blur Strength — Use the Blur Radius slider to choose how strong the blur should be — 5 px for subtle softening, 30+ px for full anonymization.
- Pick Brush Size — Larger brush for broad areas like backgrounds; smaller for precision around faces or text.
- Paint to Reveal Blur — Drag the brush over areas you want blurred. Switch to Eraser mode to refine edges or remove blur from areas you didn't mean to cover.
- Download — Export the result at the original resolution as JPG or PNG. Everything happens locally in your browser.
Who should use this
Journalists redacting source materials, parents sharing family photos publicly, real-estate professionals hiding house numbers, e-commerce sellers softening backgrounds, social-media users protecting identity of people in the frame, and photographers faking portrait bokeh on cellphone shots.
How to get started
Upload a photo. Set blur radius to 18 px and brush size to 80 px. Paint over the area you want blurred — say, the background behind a person. Switch to Eraser if you accidentally blur into the subject. Download.
Best practices
- For privacy: 25+ px blur radius makes faces & text unrecognizable
- For aesthetic background blur: 12–18 px gives natural bokeh feel
- Paint slower for stronger mask coverage in one pass
- Use Eraser for fine work around hair and irregular edges
- Increase blur radius progressively if subject background is far
- For portraits, leave a tight outline around the subject for cleanest results
Pro tips
- Blur radius 15–20 px is enough to hide identifying detail like faces or text.
- Use a soft, feathered brush near edges to avoid hard cutoff lines.
- Switch to Eraser to refine the mask without starting over.
- For portrait-style background blur, paint everything except the subject.
- For privacy redaction (faces, plates), 30+ px radius is recommended.
- Increase brush size for broad strokes, decrease for fine-tuning hair edges.
Expert insights
⚡ Privacy Pro Tip
For true anonymization, use radius 30+. Studies show that blur under 15 px can sometimes be reversed by AI — go big when privacy matters.
🎯 The Three-Layer Trick
We pre-blur the entire image once, then use the mask to reveal it. This is why the brush feels instant — it's not blurring on every stroke, it's just unhiding.
✓ Real Workflow
Photojournalists use this exact technique to redact bystanders' faces before publishing — fast, reliable, and works offline.
⭐ Pro Bokeh
For convincing fake bokeh: 14 px radius, paint everything except subject, then use Eraser at 30% brush size to clean up subject edges. Looks like an 85mm f/1.4.
Limitations to be aware of
- Blur uses CSS-filter blur — extremely large radii (50+ px) may slow the preview on very high-res images
- Mask is binary at the edge of brush radius (smoothly gradient inside)
- No per-stroke undo (use Eraser or Clear Mask)
- Touch precision on mobile is limited; desktop offers best control
- Cannot blur with motion or radial blur — use dedicated tools for those
Frequently asked questions
- How is this different from a regular blur tool?
- A regular blur applies uniformly across the entire image. Selective blur lets you choose exactly which parts get blurred — perfect for fake-bokeh portrait effects or privacy redaction without affecting the whole photo.
- Can I use this for privacy?
- Yes — it's commonly used to anonymize faces, license plates, addresses, and screen contents in screenshots before sharing online. Use a blur radius of 25+ px for true unrecognizability.
- Why is the blur looking weak?
- Two reasons: (1) blur radius is too low — try 15+ px; (2) the brush passed too quickly — paint slower or paint twice over the same area to build up mask opacity.
- Can I undo specific strokes?
- This tool offers Eraser mode to remove blur from areas, and Clear Mask to start over completely. For per-stroke history, use the Photo Editor.
- Does it preserve image quality?
- Yes. The base image stays sharp, and only the painted areas are blurred. On download, everything is rendered at the original resolution.
- Is my image uploaded anywhere?
- No. The entire workflow uses your browser's Canvas API. No server upload, no data collection — completely private.
- Will it work on phones?
- Yes, the canvas accepts touch input. Desktop with a mouse or stylus offers best precision, especially for fine masking.
- Can I create depth-of-field bokeh effects?
- Yes — that's a popular use. Paint over everything except your subject, set radius around 20–25 px, and you get a convincing fake-bokeh portrait look.