Sharing images publicly has become a reflex — screenshots posted to social media, photos shared in blog posts, product images uploaded to listings, documentation shared with clients. But most images captured in the real world contain things you shouldn't share: faces of people who didn't consent, license plates, home addresses, financial account numbers, email addresses visible in screenshots, confidential information in background documents.

Blurring or censoring specific areas of an image before sharing is a basic privacy and security practice, and it takes about thirty seconds with the right tool. Here's how to do it, what the different techniques accomplish, and when each is appropriate.

The Tools: Blur vs. Pixelate vs. Black Box

There are three common approaches to obscuring part of an image, and they're not interchangeable:

Gaussian blur spreads pixel values outward in a smooth gradient, producing a soft, out-of-focus effect. It looks natural and unobtrusive — a blurred face in a crowd photo reads as intentional and considered rather than aggressively redacted. The risk with blur is that at low blur radius values, determined individuals can sometimes use deconvolution algorithms to partially recover the original content. For faces and backgrounds, this is rarely a practical concern. For sensitive text like account numbers or passwords, use a higher blur radius or opt for pixelation instead.

Pixelation reduces a selected area to large, blocky pixels — the classic "mosaic" censor effect familiar from news footage and true-crime documentaries. Pixelation is more visually emphatic than blur and communicates clearly that the area has been deliberately redacted. For text and numbers specifically, pixelation at a sufficiently large block size is more reliably unrecoverable than blur. The larger the pixel blocks, the more secure the redaction.

Solid fill (black box) replaces the selected area with a solid color, most commonly black. This is the most complete and unambiguous redaction method — there is no residual information in a solid fill. It's the standard approach in legal and official document redaction. Visually, it's more jarring than blur or pixelation, which makes it the right choice when privacy or security is the primary concern and aesthetics are secondary.

How to Blur Part of an Image Online

The Pixelate & Censor tool on ImageToolShack handles selective blurring and pixelation entirely in your browser — your image never leaves your device, which matters when the content you're redacting is sensitive.

1. Upload your image. The tool accepts JPG, PNG, and WebP. For screenshots with text, PNG is preferable since it's lossless — JPEG compression can make text edges less sharp before you've even started editing.

2. Select the area to blur. Draw a selection rectangle over the region you want to obscure. Most tools let you draw multiple selections to handle several regions in one pass — useful if you're redacting multiple faces or several instances of sensitive data in a single screenshot.

3. Choose blur or pixelate, and set the intensity. For faces: Gaussian blur at medium-to-high radius, or pixelation at a block size large enough that facial features are completely unreadable. For text: pixelation at a large block size, or solid fill. For backgrounds: Gaussian blur at a lower radius to create a soft background separation effect without looking obviously redacted.

4. Export. Download as JPG or PNG. For images containing text, export as PNG to avoid JPEG compression re-introducing artifacts around the blurred areas.

For background softening specifically — where you want to emphasize a subject by blurring everything around it rather than redacting a privacy concern — the Sharpen & Blur tool gives you full-image blur control, which you can combine with background removal for a cleaner separation effect.

Common Use Cases

Blurring faces in photos. The most common privacy redaction need. Apply to any identifiable person who hasn't consented to be in a publicly shared image — bystanders in street photography, children in event photos, individuals in screenshots of public spaces. Use Gaussian blur at a radius that makes facial features fully unreadable. A face at 150px wide needs a blur radius of at least 15–20px to be reliably obscured.

License plates. Always blur or pixelate license plates before sharing photos of vehicles publicly. License plates can be used to look up registered owner information in some jurisdictions. This applies to your own vehicle as much as others — a photo of your car in front of your home with a readable plate is more locating information than most people intend to share.

Screenshots containing personal information. The most underestimated redaction need. When you screenshot an email to share a funny exchange, the email addresses are visible. When you screenshot a conversation to show a friend, the contact names and photos are visible. When you screenshot a banking notification, the partial account number is visible. Get into the habit of redacting before sharing — pixelation or solid fill for any text that identifies you or others.

Addresses and location information. Screenshots of maps, delivery confirmations, and calendar events often contain home or work addresses. Blur or pixelate these before sharing in any public or semi-public context.

Children in photos. Many parents and educators choose to blur or obscure children's faces when sharing photos publicly online. This is a personal privacy decision rather than a legal requirement in most contexts, but it's a widely adopted practice for images shared on social media or websites.

Background blur for portrait emphasis. Separate from privacy redaction entirely — blurring the background of a portrait or product photo to simulate shallow depth-of-field is a common editing technique. Smartphone cameras do this automatically with portrait mode, but for photos taken without it, or to apply the effect to older images, the Sharpen & Blur tool provides the control needed. Pair it with the Background Remover for a cleaner subject isolation before applying selective blur.

A Note on Redaction Security

Not all blur is equally secure for sensitive text. This is worth understanding before you share anything with genuine privacy implications.

Low-radius Gaussian blur on text can be partially reversed by image processing algorithms, particularly if the original text is high-contrast and the blur radius is insufficient. Studies have demonstrated that blurred text in screenshots can sometimes be recovered if the blur is light. The practical mitigation: use a high blur radius (enough that the text area looks uniformly smudged with no readable character shapes), use pixelation with large block sizes, or use solid fill.

Pixelation at large block sizes (where each block is larger than an individual character) is more resistant to recovery than blur, because the averaging process loses more of the original spatial information.

Solid fill is definitive — nothing is recoverable from a region that has been filled with a flat color.

One more thing worth knowing: blurring in a JPEG and then re-saving as JPEG introduces compression artifacts. These artifacts don't recover the original content, but they can make the boundary of the blurred region slightly more apparent. For sensitive redactions, export as PNG.

Blurring Backgrounds for Creative Effect

Beyond privacy, blur is one of the most-used creative tools in photography post-processing. The shallow depth-of-field look — sharp subject, soft background — is the signature of professional portrait and product photography, and it's achievable in post even when the original image was shot at a narrow aperture.

The workflow for background blur as a creative effect: use the Background Remover to isolate the subject, apply blur to the background layer only, then recombine. This is a multi-step process that produces a cleaner result than applying blur to the full image with a selection, because the subject edges stay sharp while everything behind them softens.

For finer control over blur radius, feathering, and masking at the subject edges — the kind of control that makes the transition between sharp subject and soft background look natural rather than cut-out — a dedicated photo editor gives you layer-based workflow that browser tools can't replicate.

For straightforward privacy redaction and quick background softening, the Pixelate & Censor and Sharpen & Blur tools handle the job free, instantly, and without your image ever leaving your device.