HeaderMod

A Chrome, Edge, and Firefox extension that modifies HTTP request and response headers per profile. A clean Manifest V3 rebuild of the header-modifier workflow, built on the declarativeNetRequest API.

Privacy Policy

• Chrome Web Store
• Firefox Add-ons
• Edge Add-ons: submission in progress — link will be added once approved.

Features

• Multiple named profiles of request/response header rules
• Per-rule enable/disable
• URL filters (regex) and resource-type filters
• Tab lock — apply a profile only to the active tab
• Pause / resume all rules without deleting them
• Cloud backup — timestamped profile snapshots via chrome.storage.sync
• Import / export profiles as JSON

Folder structure

chrome/    MV3 source for the Chrome Web Store (declarativeNetRequest, service worker)
edge/      MV3 source for Microsoft Edge Add-ons (identical to chrome/ — same Chromium engine)
firefox/   MV3 source for Firefox Add-ons / AMO (declarativeNetRequest, background scripts + gecko settings)
docs/      GitHub Pages site (landing page, privacy policy)

chrome/ and edge/ are byte-for-byte identical — Edge is Chromium-based and uses the same Manifest V3 background.service_worker model, so no manifest changes are needed. A dedicated edge/ folder (rather than reusing chrome/) exists only so each store package can be built, versioned, and submitted independently. firefox/manifest.json is the one file that actually differs:

• Chrome / Edge use background.service_worker.
• Firefox uses background.scripts (Firefox has no extension service worker) and adds browser_specific_settings.gecko (extension id headermod@ibaciu6, strict_min_version 128.0 — the baseline for declarativeNetRequest session rules and modifyHeaders).

All other runtime files (background.js, popup, scripts, styles, images) are identical across all three.

Build the store packages

cd chrome  && zip -r -X ../dist/headermod-1.0.0-chrome.zip  . -x '.*'
cd edge    && zip -r -X ../dist/headermod-1.0.0-edge.zip    . -x '.*'
cd firefox && zip -r -X ../dist/headermod-1.0.0-firefox.zip . -x '.*'

Load unpacked for testing

• Chrome: chrome://extensions → Developer mode → Load unpacked → select chrome/.
• Edge: edge://extensions → Developer mode → Load unpacked → select edge/.
• Firefox: about:debugging → This Firefox → Load Temporary Add-on → select firefox/manifest.json.

Privacy

HeaderMod transmits no data to the developer or any third party. Profiles and settings are stored locally (and synced across your own browser profile via chrome.storage.sync if browser sync is enabled). See the Privacy Policy.

License

MIT