Header Injector

Intercept HTTP/HTTPS requests and inject custom headers based on configurable URL filters.

The extension allows the user to define rules for modifying HTTP/HTTPS headers (adding, editing, or removing headers) that are automatically applied to network requests matching user-configured URL filters, while displaying the currently active rules in the popup. Built for developers who need to simulate API clients, test gateway rules, or validate backend behavior with specific headers. Key features: - URL filter matching with AND / OR logic - Optional URL exclude rules - Custom request headers per configuration - Global ON/OFF toggle - Optional Recent Matches log (up to 100 stored entries; popup shows the latest 20) - DevTools helper for quick inspection, commands on console: - HeaderInjector() - HeaderInjector('config') - HeaderInjector('log') - HeaderInjector.clear / HeaderInjector('log').clear / HeaderInjector('config').clear - Local storage only (no remote sync or external servers) How it works: - You configure filters and headers in the popup - The extension applies rules in the browser - Matching requests are logged for debugging Privacy: - Data is stored locally in your browser storage - No analytics, no telemetry, no external data collection Intended use: - Development, QA, staging, and local debugging environments