HeaderNinja - HTTP Header Editor

Add, change, or remove HTTP request headers on the sites you choose. Runs locally, no account, no tracking.

HeaderNinja lets you add, change, or remove HTTP request headers on the sites you choose, straight from the Chrome toolbar. No proxy, no DevTools, no account. TYPICAL USES • Send an Authorization or bearer token to an API you are testing • Set a custom User-Agent to see how a site behaves on other devices • Pass a feature flag or debug value to a staging server • Reproduce a bug that only appears with a specific request header • Try out CORS, caching, or content-negotiation behaviour by hand FEATURES • Add or override any request header by name and value • Optional URL filter per rule, so a value applies only where you want it • One-click switch to enable or disable every rule at once • Rules are saved locally and survive browser restarts • Small, focused popup with no sign-up, paywall, or upsell HOW IT WORKS HeaderNinja uses Chrome's declarativeNetRequest API (Manifest V3), so your rules are applied by the browser's own network layer without the performance and privacy cost of the older blocking webRequest approach. Everything is stored in your browser. PRIVACY • No tracking, analytics, or telemetry • No data leaves your browser • No remote code • Two permissions only: declarativeNetRequest to apply your rules, and storage to save them Built for developers, QA engineers, and anyone who tests APIs. Free and open source under the MPL-2.0 licence.