A web application firewall inspects and filters HTTP traffic to help protect web applications from malicious or unwanted requests.
A web application firewall, or WAF, is a security control that inspects and filters web traffic. In plain language, it sits in front of a web application and helps detect or block suspicious HTTP requests before they reach the application itself.
A WAF matters because public web applications are exposed to constant probing and misuse attempts. Even when the application team is improving secure coding and patching, a WAF can add another layer of visibility and protection around web-specific traffic patterns.
It also matters because web attacks often look different from general network traffic issues. HTTP requests, headers, parameters, and payload patterns may need controls that are more application-aware than a basic network firewall rule set.
WAFs appear in front of internet-facing websites, APIs, customer portals, and cloud-hosted applications. Teams use them to support detection and filtering for suspicious request patterns, to reduce some common web-exposure risk, and to buy time while deeper application fixes are made.
Security teams review WAFs during application launches, incident response, rule tuning, and exposure reduction work. They care about false positives, coverage boundaries, and whether the WAF is being treated as a helpful layer rather than a substitute for secure application design.
A retail website experiences repeated suspicious requests that target login and form inputs. The WAF adds rate controls, request inspection, and blocking logic for those patterns while the application team also reviews the underlying code and authentication protections.
A WAF is not a replacement for fixing insecure application behavior. It can reduce exposure and improve visibility, but it should not be treated as proof that the application itself is free from weaknesses.
It is also different from a general Firewall. A basic firewall filters broader network traffic, while a WAF focuses on web-layer requests and web-application behavior.