Redaction vs sanitization: what's the difference when releasing a classified document?

When a classified document is prepared for release, two related but distinct processes often come up: redaction and sanitization. They overlap in practice, but they answer different questions. Redaction asks, what specific information must be removed from this document? Sanitization asks, what must be done to this document so it can safely exist at a lower classification or in public hands?

Redaction

Redaction is the targeted removal or masking of specific portions of a record while leaving the rest intact. A reviewer examines the document line by line and obscures only the words, names, or passages that remain protected — for example, classified national-security details or personal privacy information.

Key characteristics:

• It operates at the level of individual pieces of information.
• The surrounding, releasable text stays visible.
• The goal is to release as much as possible while withholding only what an authority or exemption genuinely protects.

In a FOIA context, redaction is how an agency releases the reasonably segregable non-exempt portions of a record after withholding the exempt material.

Sanitization

Sanitization is the broader process of transforming a classified document into a version that is safe to release or to handle at a lower classification level. It includes redaction, but it also addresses whether what remains — taken as a whole — still reveals protected information.

Sanitization considers:

• Aggregation and mosaic risk: individually harmless facts that, combined, reveal something classified.
• Context and inference: what a reader could deduce from what is left, including sources and methods.
• Residual markings and metadata: classification banners, portion marks, or hidden electronic data that must be removed or corrected.

A properly sanitized document is one whose remaining content can stand on its own at the new, lower level without exposing anything still protected.

Why the distinction matters

Redaction is a technique; sanitization is the outcome you are trying to achieve. You can redact specific lines yet still fail to sanitize a document if the surviving text allows protected information to be reconstructed. Treating the two as identical is a common source of inadvertent disclosure.

Both depend on a clear declassification decision and a knowledgeable reviewer who understands what is protected and why. To learn more, see the declassification topic hub.