Trusted URL allowlisting is a security control that lets a system open or send traffic only to a preapproved set of web addresses, domains, or endpoints. Anything outside the allowlist is blocked or requires review. It is commonly used in browsers, email gateways, API clients, and AI agents that can generate links or make outbound requests.
In cyber security, this matters because many attacks depend on redirecting users or automated systems to malicious destinations. Allowlisting reduces phishing, command-and-control callbacks, data exfiltration, and prompt-injection abuse that tries to make an AI agent fetch attacker-controlled content. It is most effective when paired with least privilege, URL normalization, and logging, because attackers often hide dangerous destinations behind redirects, subdomains, or lookalike domains. Used well, trusted URL allowlisting helps keep automation from crossing from internal trust into the open internet without control.