API Header Manager

API Header Manager lets you add, modify, or remove HTTP headers on both requests and responses, right from your browser. Organize your headers into profiles and scope them to specific URLs — ideal for testing APIs, injecting auth tokens, simulating headers, or debugging without touching your backend. ★ FEATURES • Request & response headers — with Set, Append, and Remove operations. • Multiple profiles — create color-coded profiles and enable or disable them independently. All active profiles apply at once. • URL filters — scope each profile by text match ("contains") or by regular expression. With no filters, headers apply to every URL. • Global pause — turn everything on or off with a single switch, without deleting your setup. • Per-header toggle — enable or disable each header individually. • Import / Export — share your full configuration as JSON with your team. On import, choose to replace everything (restore) or merge with your current profiles. • ModHeader compatible — automatically detects and converts profiles exported from ModHeader. • Multi-language — English, Spanish, and Portuguese (auto-selected from your browser language). • Modern UI — clean design with automatic light and dark mode. ★ PRIVACY 100% local. API Header Manager does not collect or transmit any data. All your configuration stays in your browser (chrome.storage.local). ★ HOW IT WORKS Built on Chrome's declarativeNetRequest API (the supported mechanism in Manifest V3 for modifying headers). Click the toolbar icon, add a header name and value, pick an operation, optionally add a URL filter, and you're done — changes apply automatically.