How to Redact Images: Blur and Black-Box Sensitive Content
Sharing a screenshot often means sharing more than you intended. Account numbers, email addresses, names, license plates, internal URLs — details that are visible in the image but should not be visible to the recipient. Redaction is the step that removes them. This guide covers how to redact images effectively: which mode to use for which content type, why processing locally in your browser matters for sensitive images, and the common workflows where redaction is needed.
Blur vs Black Box: Choosing the Right Redaction Mode
Blur applies a mosaic pixelation effect. The viewer can tell that something was in that area but cannot read it. This is appropriate for faces in photographs, license plates in street-level images, and background content in screenshots where the viewer needs context but not the specific detail. Blur is visually natural — it looks like a deliberate obscuring choice rather than a harsh edit.
Black box replaces the area with a solid black rectangle. No shape, no hint, no residual. This is the standard for document redaction in legal, compliance, and business contexts. If you are removing a name from a contract, an account number from a support screenshot, or a confidential figure from a financial document, black box is the correct choice. Any residual visual information is a redaction failure — use black box when the content must be completely gone.
Why Local Processing Matters for Sensitive Images
The typical flow for an online image tool is: upload the file to a server, process it, return the result, delete (maybe) the original. For general-purpose images, this is an acceptable tradeoff. For images containing personally identifiable information, confidential business data, or legally protected content, this upload step is a meaningful risk. Your original unredacted image travels to a server you do not control before any redaction is applied.
Tracelyx Redact processes entirely in your browser. The image loads into browser memory, redaction layers are applied on a local canvas, and the output PNG is generated on your device. Nothing is transmitted. The server never sees your image — before or after redaction. For support teams handling customer data, legal teams working with protected documents, and anyone processing content with privacy obligations, this distinction matters.
Step-by-Step: Redacting a Screenshot
- Upload the screenshot — Drop the file onto the tool or click to select it.
- Choose Black box mode — For text content in screenshots, Black box is almost always correct.
- Adjust brush size — Use a larger brush for wide areas like full lines of text; smaller for isolated numbers or addresses.
- Draw over each sensitive area — One pass per area. Use Undo last if you overshoot.
- Download the PNG — The redaction is permanently applied. The output file has no record of the original content.
Common Workflows
Customer support teams: redact account numbers, order IDs, and customer names from screenshots before adding them to shared tickets, Slack channels, or email threads. A single redaction pass before sharing keeps PII out of systems where it does not belong.
Social media: remove license plates, house numbers, faces, and contact details from photos before posting. Open the tool, draw over the details, download, post. No app, no account, no upload — under a minute for most photos.
Start Redacting
Tracelyx Redact is free, requires no account, and processes your image entirely in your browser. Upload a screenshot or photo, draw over what should not be visible, and download the result. The redaction is permanent and your original image never leaves your device.
Try Tracelyx Redact now →
