Image Blur Tool — soften or redact photos in your browser

The image blur tool lets you soften an entire photo or blur just one selected rectangle — a face, a license plate, a document, an address label — directly in your browser, with no software to install and no file ever leaving your device.

Arb Digital built this as part of a growing set of free, privacy-first image tools. Whether you're softening a background for a more professional look or redacting private information before posting a screenshot online, this tool handles it in seconds.

What This Image Blur Tool Does

This tool offers two distinct modes. "Blur whole image" applies a uniform Gaussian-style blur across every pixel, controlled by a radius slider — useful for soft background effects, dreamy photo styles, or de-emphasizing a busy backdrop. "Blur selected area only" lets you click and drag directly on the preview to draw a rectangle over exactly the region you want obscured, leaving the rest of the photo perfectly sharp. This second mode is specifically built for redaction: covering a face, a car's license plate, a visible ID number, an email address in a screenshot, or any other sensitive detail before you share an image publicly.

Both modes update live as you move the radius slider, so you can dial in exactly how strong the blur needs to be — light enough to just soften texture, or strong enough to make a face completely unrecognizable.

How to Use the Image Blur Tool

1. Upload your photo. Click "Choose an image" or drag a file onto the drop zone.
2. Pick a blur mode. Choose "Blur whole image" for a uniform soft effect, or "Blur selected area only" to redact one specific region.
3. Adjust the radius slider. Start around 8-15px for a subtle effect, or push to 25-40px for a strong, fully obscuring blur.
4. If using selection mode, drag on the preview. Click and drag directly over the face or detail you want to hide; you can clear and redraw the selection as many times as needed.
5. Download your result. Choose PNG, JPEG, or WebP and click "Download Image."

How the Blur Effect Is Calculated

This tool uses the browser's native Canvas 2D filter API, specifically the CSS-style blur(Npx) filter applied directly to the canvas rendering context. Behind the scenes, this performs a Gaussian blur — a well-established image-processing technique that replaces every pixel with a weighted average of its neighboring pixels, where nearby pixels count more heavily than distant ones. A larger radius means the tool samples from a wider neighborhood of surrounding pixels, which is why higher radius values produce a stronger, more diffuse blur that can completely erase fine detail like facial features or small text.

For the redaction (selected area) mode, the tool first renders a fully blurred copy of the entire image on a hidden canvas, using the true surrounding pixels for an accurate, edge-free blur — then copies only the pixels inside your selected rectangle from that blurred copy onto the sharp original. This two-layer technique avoids the washed-out or oddly bordered look that comes from blurring an isolated crop in complete isolation, since the blur calculation still has real neighboring image data to draw from at the edges of your selection.

Redacting Private Information Safely

Blurring is one of the most common ways people try to hide sensitive information in a screenshot or photo before posting it online — a face in a crowd photo, a home address on a package label, a license plate, a phone number, or an account number on a statement. It's worth knowing that a light blur is not always a strong enough safeguard: heavily blurred text can sometimes still be partially reconstructed with enough contrast or pattern-matching effort, particularly at low blur radii. For genuinely sensitive information, use a strong blur radius (30px or higher relative to how large the detail appears in your image) or, better yet, fully black out the area with an opaque rectangle rather than relying on blur alone. This tool's high radius settings are built to make details thoroughly unrecognizable, but always double-check the result at full zoom before sharing anything sensitive publicly.

Because everything happens locally, using this tool for redaction is itself a privacy-safe workflow: the sensitive image never gets uploaded to a third-party server in the first place, unlike some "free" online redaction tools that require a file upload before they'll process anything.

Common Use Cases

• Blurring faces in a group photo before posting publicly, for privacy or consent reasons.
• Redacting license plates in photos of vehicles or parking lots.
• Hiding personal details in screenshots — email addresses, phone numbers, order numbers, or ID cards.
• Softening a busy background behind a product or portrait for a more professional, magazine-style look.
• Creating a depth-of-field effect by blurring the whole image and layering a sharp cutout in design software afterward.
• Blurring a watermark placeholder area for a mockup or draft design review.

Why This Runs Entirely in Your Browser

Redaction tools handle inherently sensitive material — faces, documents, and personal identifiers — which makes the "where does my file actually go" question more important than usual. Many free online blur and redaction tools require uploading your image to their servers before returning a processed copy, meaning the very information you're trying to hide is briefly (or permanently) stored somewhere outside your control. This tool never uploads anything. The image is read locally via the browser's FileReader API, all blurring math runs through the Canvas 2D filter and drawing APIs inside your own browser tab, and the final download is generated locally using canvas.toBlob() with a temporary object URL that is revoked right after the download begins. Close the tab and nothing remains on any server, because nothing was ever sent to one.

Common Mistakes to Avoid

• Using too low a blur radius for redaction — a light blur can sometimes still leave a face or text partially recognizable; use a strong radius (25-40px) for anything genuinely sensitive.
• Drawing the selection rectangle too tightly around the face or detail — leave a small margin so no unblurred edge peeks out.
• Forgetting which mode is active — check the "Mode" indicator in the results panel before downloading, so you don't accidentally blur the whole image when you only meant to redact one area.
• Saving as JPEG when transparency is needed — JPEG does not support transparent backgrounds; use PNG or WebP instead.
• Assuming a blurred image can be un-blurred later — once downloaded, the blur is permanently baked into the pixel data; always keep your original file if you might need the sharp version again.

Related Free Tools From Arb Digital

Pair this tool with the Brightness & Contrast Tool to adjust exposure before or after blurring, the Grayscale Converter for black-and-white conversions, the Image Rotate & Flip tool to fix orientation first, or the Image Resizer and Image Cropper for sizing and framing. See our full free online tools hub for more.

Frequently Asked Questions

Whole-Image Blur for Creative Effects

Beyond redaction, a uniform whole-image blur has plenty of creative uses. Designers often blur a background photo heavily and layer bold white text on top for a hero banner, since the softened backdrop keeps text legible without needing a separate dark overlay. A light blur (5-10px) can also make a slightly grainy or low-resolution photo look intentionally soft rather than simply "blurry by accident," which is a common trick in lifestyle and wellness branding. On the other end of the scale, a very heavy blur (30px+) turns any photo into an abstract wash of color and shape — useful as a placeholder background, a loading-state image, or a subtle textured backdrop that never competes with foreground content.

Because the radius slider updates the preview instantly, it's easy to experiment: start at a low value and increase it gradually until the effect matches what you have in mind, whether that's a barely-there softness or a fully abstracted color field.

Blur Radius, Image Size, and What "Enough" Really Means

One detail that trips people up: blur radius is measured in absolute pixels, not as a percentage of the image. That means the same 20px radius will look dramatically stronger on a small 400×300 thumbnail than on a large 4000×3000 photo straight from a modern phone camera, since 20 pixels covers a much larger fraction of the smaller image. If you're working with a high-resolution photo and a face only takes up a small portion of the frame, you may need a much higher radius value than you'd expect — sometimes 30-40px or more — to fully obscure detail. A quick way to judge this: zoom into the preview at 100% (or view the downloaded file at its native size) and confirm the redacted area is genuinely illegible before sharing it anywhere public. Trusting a preview that's been scaled down to fit the screen can be misleading, since a shrunk-down blurred face can look more obscured than it actually is at full resolution.

Selection Mode: Precision Without Complexity

The redaction mode is intentionally simple: one click-and-drag defines one rectangle, and that rectangle is exactly what gets blurred. There's no complex lasso tool, no multi-point polygon to fuss with, and no separate "apply" button to remember — the blur updates the moment you release the mouse or lift your finger on a touchscreen. If your first attempt doesn't line up perfectly with the face or detail you're hiding, "Clear Selection" resets it instantly so you can redraw. For a slightly larger or more oddly shaped area — say, a face partially turned at an angle — simply drag a rectangle generously larger than the feature itself; the resulting blur radius will fully obscure detail well within the rectangle's boundary, so a small margin of extra coverage costs nothing but a slightly larger blurred patch.

This tool runs entirely in your browser using built-in JavaScript. Your images are never uploaded, stored, or sent to any server.