HeaderSmith — Modify HTTP Request & Response Headers

A simple MV3 alternative to ModHeader. Add, edit & remove HTTP request & response headers by URL. Import your ModHeader rules.

HeaderEditor lets you create rules to inject, modify, or remove HTTP request headers for specific URL patterns — without a proxy server or writing code. Set Authorization headers for API testing, spoof User-Agent strings for compatibility testing, add CORS headers for local development, or block tracking headers. **Key Features:** - Rule-based header injection using URL patterns (glob and regex) - Inject, modify, or remove request headers - Pre-built templates: Authorization Bearer, User-Agent presets (mobile/desktop/bot) - Rules toggle on/off individually or all at once - Import/export rules as JSON for team sharing - Works with fetch, XHR, and any browser request - No proxy setup required — works at the browser extension level **Who is it for?** Backend developers testing APIs that require auth headers, frontend developers working around CORS in local development, QA engineers testing responsive behavior with User-Agent spoofing, and security researchers studying header-based access control. **Privacy & Trust:** All rules are stored locally in your browser. No header data, URLs, or rule configurations are sent to external servers. Anonymous analytics via Google Analytics 4 only. Install HeaderEditor — debug faster without leaving Chrome.