Header Override

Modify HTTP request headers, ModHeader-style (Chrome MV3 / declarativeNetRequest)

Header Override is a developer-focused browser extension that lets you modify outgoing HTTP request headers without leaving the browser. Define profiles of header rules, toggle them on and off, and target specific URLs with glob or regex patterns. Designed for developers and QA engineers who: • Test APIs with multiple Bearer tokens for different roles, environments, or users • Inject custom headers into Swagger UI, OpenAPI explorers, or any browser-based tool • Bypass simple authentication during local development • Switch between dev / staging / prod environments without juggling browser profiles Key features: • Profiles with independent on/off toggle and color badge • Per-rule operations: set, append, or remove a header • URL conditions — glob (*://*.example.com/*) or regex (/^https:\/\/api\./) at profile and rule level • Multi-preset rules — keep N values for the same header (e.g. SUPERVISOR / OPERATOR tokens) and switch via dropdown • Per-tab override — lock a profile to a single browser tab • JWT decoder + editor — click the dot next to an Authorization Bearer token to decode header/payload, see expiry status, edit and re-encode JSON • ModHeader v2 JSON import/export — full round-trip, with auto-collapse of duplicate-header rules into presets • Paste cURL — drop a curl command, get a profile with all its headers in one click • Test URL sandbox — type a URL, see which rules match, optionally fire a real fetch • Recent matches Activity log • Light / dark / auto theme (follows OS preference) • Hotkeys — Ctrl+Shift+H toggles all overrides, Ctrl+Shift+U opens the popup Privacy: all data is stored locally. The extension does not collect, transmit, or share any user data. Source code: https://github.com/reservation-extension/source-header-override Privacy policy: https://github.com/reservation-extension/privacy-header-override/blob/main/PRIVACY.md