Fuzzing is automated testing that sends large volumes of varied, malformed, or unexpected inputs into software to expose crashes, hangs, memory corruption, and logic flaws. Instead of relying on a small set of hand-written test cases, a fuzzer mutates files, network packets, API requests, or command-line arguments and watches for abnormal behavior.
In cybersecurity, fuzzing matters because many high-impact bugs are only triggered by unusual edge cases that normal testing misses. Attackers use fuzzing to discover exploitable weaknesses in parsers, protocols, browser engines, file handlers, and embedded software. Defenders use the same technique to harden code before release, often pairing it with sanitizers, coverage guidance, and crash triage to turn failures into actionable fixes. Good fuzzing can reveal denial-of-service conditions, memory safety bugs, and security issues early, before they become real attack paths.