Header Lens

Privacy-first Chrome DevTools extension for setting, overriding and removing HTTP request and response headers per site.

Header Lens lets you set, override, append or remove HTTP request and response headers for the site you're working on — and nothing else. WHAT YOU CAN DO • Set (override), append or remove any request or response header • Scope a rule to one site (subdomains included) or to every site you granted, with an optional URL filter • Rules run as declarativeNetRequest dynamic rules: they apply to navigations, fetches, scripts, images and websockets, and survive browser restarts • First-party by default: a rule fires for the site's own requests and navigations, not for third-party pages embedding it — opt a rule into "any origin" for cross-site API calls • Pause everything with one switch; per-rule on/off; the toolbar badge shows how many rules are active • Presets for common headers: Authorization, Accept-Language, Cache-Control, X-Forwarded-For, a mobile User-Agent, CORS / CSP / X-Frame-Options response tweaks • Profiles: save a site's rule set under a name and switch setups in one click; export/import as JSON • Sortable, searchable, filterable table with multi-select and an inline editor • Three surfaces: a popup, a DevTools panel, and a side panel that follows the tab you're on (Alt+Shift+H) PRIVATE BY DESIGN • Host access is requested per site, only when you ask, and can be revoked from Settings • Nothing leaves your device: no analytics, no telemetry, no remote resources, no account • The UI only ever receives the tab's origin — never the path or query • Credential-like values (Authorization, API keys) can be masked; exporting or copying them asks first • Rules that weaken a site's own defences (CSP, X-Frame-Options, HSTS…) are clearly badged WHO IT'S FOR Frontend and backend engineers testing auth, feature flags, locales, caching and CORS; QA engineers reproducing user states; anyone who needs a header on a request without touching server config. Header Lens is part of the Lens DevTools family (Cookie Lens, Event Lens). Open source, MIT. Docs & privacy policy: https://lensdev.tools/docs/header-lens/