Input Validation Pipeline

Input validation is the first line of defense a web application has against malformed and malicious data: every value a user submits should be checked before it is trusted. This simulator visualizes that idea as a physical pipeline — form submissions travel down a conveyor and pass through four sequential defensive stages: a type check, a length/range check, an allow-list pattern check, and an output-encoding stage. Fire off normal, malformed or injection-attempt payloads and toggle each stage on or off to see exactly which layer catches which class of bad input, and what happens — a live "passed through unsafely" counter — the moment a layer is missing.