DevHeaders - HTTP Header Editor & Modifier

Fast HTTP request-header modification for developers and testers.

DevHeaders adds or overrides HTTP request headers on the fly — no proxy, no app code changes, no DevTools workarounds. Testing against staging vs. production, trying different auth tokens, toggling feature-flag headers, or adding debug headers for an API — DevHeaders does this one thing well, with fast switching between configurations. FEATURES • Profiles — named sets of headers (key + value). Switch environments or auth scenarios with one click. • Master switch — a global on/off for all header modification, independent of the active profile. See the server's "clean" response and bring your headers back just as fast. • Per-header checkboxes — disable a single header temporarily without deleting it from the profile. • Duplicate keys, on purpose — keep several variants of the same header and toggle between them; the last enabled one wins. • Icon badge — shows master switch state and active header count at a glance, no need to open the popup. • JSON import/export — back up your profiles or hand a configuration to a teammate in one file. • Persistent storage — your profiles survive a browser restart. • Clean, modern interface with per-profile accent colors. WHY DEVHEADERS Most header-editing tools bundle in request blocking, mocking, throttling, and a dozen other features you don't need. DevHeaders focuses on one job — modifying request headers — and does it fast, with no external dependencies and no telemetry. v1 focuses on request headers. Rules apply across all sites by default. PERMISSIONS DevHeaders requests broad host permissions and declarativeNetRequest because header rules are applied directly by the browser's networking layer — not through a remote server or third-party proxy. Your header values never leave your device.