HeaderMod is a lightweight and open-source browser extension designed for Chrome that facilitates the interception and modification of outgoing HTTP requests. Users can easily inject, update, edit, or override HTTP headers on a per-URL basis, making it an essential tool for developers and testers. With features such as wildcard-based URL matching and the ability to define multiple header-modification rules, HeaderMod offers significant flexibility in managing request headers.

The extension allows users to add or replace any request header with specified names and values, and rules can be enabled or disabled individually. Additionally, it saves these rules in local storage for seamless use across browser sessions. A dynamic toolbar icon indicates which rules are active, enhancing user experience. Importantly, HeaderMod prioritizes privacy, ensuring that no personal data is collected or shared externally.