Your files never leave your device. All processing happens locally in your browser.
How do I blur or black out private information in a screenshot?
Open your screenshot in the Privacy Blur editor, draw a rectangle or brush over each sensitive area, and pick a style — strong Gaussian blur, mosaic pixelate, or a solid black box. The redaction is baked destructively into the pixels, so the hidden data is genuinely gone from the exported PNG, then you download or copy it. For anything truly sensitive (passwords, card numbers, faces) use the BLACK BOX — blur and light pixelation can sometimes be reversed. Everything runs in your browser; your image is never uploaded.
Rectangle + freehand brush tools; add as many regions as you need
Three styles: Gaussian blur, mosaic pixelate (adjustable block), or solid black box
Destructive — pixels are actually replaced, not just covered over
Use a black box for passwords / faces; blur & light pixelation can be de-blurred
100% client-side — the screenshot never leaves your browser, and export drops the original file’s EXIF
What is
Screenshot redaction (blur / pixelate / black box)
Screenshot redaction is permanently hiding sensitive content in an image by replacing the underlying pixels of the marked region. A solid black box overwrites the pixels with one opaque colour and is mathematically irreversible; a mosaic (pixelate) averages fixed-size blocks to a single colour; a Gaussian blur averages each pixel with its neighbours. Blur and light pixelation are averaging transforms and can be partially REVERSED (e.g. Depix / Unredacter), so only a black box — or very heavy pixelation — should be trusted for high-stakes data.
No. The image is drawn to a <canvas> and every blur, pixelate and black-box edit happens in your browser; the picture never leaves your device.
The Privacy Blur tool is 100% client-side. Your screenshot is loaded into an HTML <canvas>, its pixels are read and rewritten locally by a pure engine (blurEngine.ts), and the finished image is exported straight to a download or your clipboard — there is no upload, no server, no CDN and no telemetry in the path. Nothing is persisted, so closing the tab erases everything; the tool works offline once cached. Because it never transmits the image, it is safe for genuinely sensitive screenshots, unlike an online blur service that would receive your file.
Sometimes, yes. Blur and light pixelation are reversible averaging transforms — tools like Depix and Unredacter have recovered pixelated passwords and text. A solid black box cannot be reversed.
Blurring and pixelation do not delete information; they average it, and that average can be attacked. Security researchers have de-pixelated passwords, API keys and short text (Depix, Unredacter) and machine-learning models have partially recovered blurred faces and plates. The weaker the effect (small blur radius, large-but-few mosaic blocks, monospaced text on a plain background) the easier the recovery. A solid black box overwrites the pixels with one opaque colour, so there is nothing left to reconstruct. For passwords, card numbers, keys or faces you must truly hide, use the BLACK BOX (or very heavy pixelation) and always verify the exported PNG at full zoom.
Yes. Each edit is written destructively into the canvas pixels, so the exported PNG contains only the redacted pixels — the original data underneath is gone.
Unlike drawing a box in a document editor (where the content often still exists beneath the shape and can be copied out), this tool bakes the redaction directly into the bitmap: the marked pixels are replaced with the blurred, pixelated or solid-colour result before you export. The download and clipboard copy are produced from that same canvas, so the sensitive pixels are not recoverable from the output file. As a bonus, re-encoding through the canvas strips the original file’s EXIF metadata (camera, GPS, timestamps) from the exported PNG. Still verify the result yourself, because you are trusting your own aim with the brush and rectangle.
Black box overwrites pixels with one solid colour (irreversible). Pixelate averages fixed blocks (reversible if light). Blur averages neighbours (the weakest, most reversible).
A black box fills the region with a single opaque colour, destroying all detail — it is the only method that is mathematically irreversible and the right choice for high-stakes data. Pixelate (mosaic) replaces each fixed-size block with its average colour; larger blocks hide more, but small blocks or few possible inputs (like digits) can be brute-forced back. Gaussian blur mixes every pixel with its neighbours and is the weakest — it looks the most "natural" but is the easiest to reverse. Choose based on the threat: black box for secrets, heavy pixelation for a compromise between looks and safety, and blur only for non-critical, non-textual content.
Detailed Explanation
📖How It Works
What the Privacy Blur Tool Does
This tool is a screenshot redaction editor that runs entirely in the browser. The user uploads, drag-drops or pastes an image, which is drawn to an HTML canvas at its TRUE resolution. They then mark sensitive areas with a rectangle tool or a freehand brush and apply one of three styles: a strong GAUSSIAN BLUR, a mosaic PIXELATE with an adjustable block size, or a solid BLACK BOX. Every effect is written DESTRUCTIVELY into the pixels, so the hidden information is truly gone from the buffer that is exported. Undo/redo, revert, zoom and pan support precise work, and the finished image is exported as a PNG by download or copy-to-clipboard. Nothing is uploaded.
Upload, drag-drop or paste a screenshot; drawn at true resolution on a canvas
Rectangle + freehand brush to mark any number of regions
Three styles: Gaussian blur, mosaic pixelate, or solid black box
Redaction is baked destructively into the pixels, then exported as PNG
100% client-side — the image never leaves the browser
⚙️Methodology
How the Three Redaction Styles Work
A pure engine (blurEngine.ts) implements the pixel maths. BLACK BOX overwrites every pixel in the region with a single opaque colour (default #000, alpha forced to 255) — mathematically irreversible. PIXELATE partitions the region into origin-aligned blocks of the chosen size, averages each block’s RGBA, and paints the whole block that average, producing a consistent mosaic even across overlapping brush dabs. BLUR runs a 3-pass separable box blur that closely approximates a Gaussian (central limit theorem) using an O(1)-per-pixel sliding window with edge clamping, confined to the marked region so it does not bleed. The rectangle tool applies the effect to a clamped rect on mouse-up; the brush applies a circular dab along the stroke and repaints only the dirty bounding box for speed.
Black box: fill region with one opaque colour (irreversible)
Pixelate: origin-aligned blocks averaged to one colour (stable mosaic)
Rectangle commits on mouse-up; brush paints circular dabs along the stroke
Effects confined to the region; brush repaints only the dirty rect
🔧Technical Details
Local Canvas Pipeline, History and Export
The image is loaded into an HTMLImageElement and drawn to a canvas sized to its natural pixels; getImageData yields the working buffer that the engine mutates in place. Edit history is a capped stack of cloned ImageData snapshots with an index for undo/redo and a revert-to-original action. Pointer events (mouse + touch) map client coordinates to pixel coordinates via getBoundingClientRect and the canvas-to-display scale ratio, so drawing stays accurate at any zoom; a scrollable container provides pan, and a Fit control sizes the canvas to the panel. Export uses canvas.toBlob(…, ‘image/png’) for a lossless download and navigator.clipboard.write with a ClipboardItem for copy — both produced from the redacted canvas, and both re-encode pixels only, which strips the original file’s EXIF metadata.
getImageData / putImageData on a natural-resolution canvas; no server
Undo/redo via a capped stack of cloned ImageData snapshots + revert
Pointer mapping via getBoundingClientRect works at any zoom; scroll = pan
Re-encoding through canvas drops original EXIF (camera, GPS, timestamps)
⚠️Limitations
Honest Limitations
Baking the redaction into the pixels is the easy part; choosing a STRONG ENOUGH method is what matters. Blur and light pixelation are averaging transforms and can be partially REVERSED: security researchers have de-pixelated passwords, API keys and short text (Depix, Unredacter) and machine-learning models have recovered blurred faces and licence plates. The weaker the effect — a small blur radius, large-but-few mosaic blocks, or monospaced text on a plain background — the easier the recovery. For genuinely sensitive data (passwords, card numbers, keys, faces you must hide) use a SOLID BLACK BOX, or failing that very heavy pixelation, and always verify the exported PNG at full zoom before you share it. The tool also trusts your aim: it will not tell you if a region peeks out, and it does not scan the image for secrets. It is a redaction aid, not a guarantee.
Blur & light pixelation can be de-blurred (Depix / Unredacter) — not safe for secrets
ML can partially recover blurred faces and plates
Small blur radius / large-but-few blocks / plain-background text recover most easily
Use a BLACK BOX (or very heavy pixelation) for passwords, keys, card numbers, faces
Verify the exported PNG at full zoom; the tool cannot check your coverage
🔒Privacy & Security
Private by Design
Everything happens on your device. The screenshot is a local canvas buffer and the edits are in-memory pixel writes; the blur, pixelate and black-box maths, the undo history, the PNG encoding and the clipboard copy all run in the browser with no upload, no server, no CDN and no telemetry. Because the image never leaves your machine, it is safe to redact genuinely sensitive screenshots — unlike an online blur service that would receive your original file (including whatever you were about to hide). Nothing is persisted, so closing the tab erases it; the tool works offline once cached. The only optional network use anywhere on the site is consent-gated ads, which never see your image.
Image and edits processed locally; no upload, server, CDN or telemetry
Safe for sensitive screenshots, unlike an online blur service
Nothing persisted — closing the tab erases everything
Works offline once cached
Only optional network use is consent-gated ads that never see the image
Screenshot redaction methods compared
Method
How it hides
Reversible?
Use for
Solid black box
Overwrites pixels with one opaque colour
No — irreversible
Passwords, keys, card numbers, faces
Heavy pixelation
Averages large mosaic blocks
Hard, but possible
A looks/safety compromise
Light pixelation
Averages small mosaic blocks
Yes — Depix / Unredacter
Non-critical content only
Gaussian blur
Averages each pixel with neighbours
Yes — the weakest
Decorative / non-sensitive areas
Only a solid black box is safe for high-stakes data; blur and light pixelation can be reversed. Everything here runs locally in the browser. As of July 2026.
