API enumeration is a cybersecurity technique where attackers systematically probe an application's API endpoints to discover available features, resources, or vulnerabilities. By sending automated or manual requests, attackers can map out the structure of the API, identify exposed endpoints, and potentially uncover sensitive data or security weaknesses. This process is often a precursor to more targeted attacks, such as exploiting discovered vulnerabilities or abusing undocumented features. Effective API security involves monitoring for enumeration attempts, implementing proper authentication, and minimizing unnecessary endpoint exposure to reduce the attack surface.