blacklistwhitelist

Blacklist and whitelist are terms used to describe lists that govern access or filtering in information systems. A blacklist contains items that are prohibited or blocked, while a whitelist lists items that are explicitly allowed or trusted. When an entity matches a blacklist entry, access is denied; when it matches a whitelist entry, access is granted. These concepts appear in domains such as email filtering, network security, software deployment, and content moderation.

The terms have historical roots in color symbolism, with black often used to indicate negative or excluded status and white to indicate positive or included status. The exact origins are obscure, but the model is consistent across contexts. In practice, the function is a deny/allow mechanism that can be expressed in policy rules and access-control lists.

There is ongoing discussion about terminology due to negative connotations associated with race and oppression. Many organizations are moving toward neutral alternatives such as allowlist and denylist, or blocklist and safelist, with variants like blocklist/allowlist and safelist/denylist. The functional meaning remains the same, but wording choices can affect clarity and inclusivity in documentation and training.

Examples: An email server may block domains on a blacklist and permit those on a whitelist; a firewall may block certain IP addresses while permitting known safe IPs; a software repository may only install packages from an allow/whitelist. This framing describes the concept of lists used to control access and filtering.