FetchGate by simddev

FetchGate bridges an external process to a live, logged-in browser tab — run authenticated fetch() calls or arbitrary JavaScript inside the tab, inheriting its full session state.

When you are logged into a website, the browser holds session state (cookies, tokens, TLS client certificates) that is not directly accessible to an external program. FetchGate bridges that gap by turning an armed browser tab into a programmable endpoint for your code.

Two modes:

• Fetch mode — your code sends a request spec; the extension executes the corresponding fetch() inside the active tab and returns the full HTTP response, inheriting all session state automatically. No credentials need to be extracted or replayed.

• JS mode — your code sends a JavaScript snippet; the extension executes it as an async function body inside the tab and returns the result. This lets you traverse the DOM, call internal APIs, or run logic that depends on live page state.

Target use case: extracting your own data from websites that have accounts but no public API, or that actively block third-party HTTP clients.

Control:

• Toolbar popup — four states: Disarmed, Armed, Host disconnected, Armed on other tab. Each state shows a single context-appropriate action button.

• Keyboard shortcut — default Ctrl+Shift+F, fully configurable from the popup. Includes a verification step that confirms the key is actually delivered by Firefox and the OS (some combinations are silently captured before the extension sees them).

Three native host implementations:

• Java host — persistent TCP server on localhost:9919; callers connect in any language.

• Python TCP host — drop-in Python replacement for the Java host; no JDK required.

• Python embedded host — your Python script IS the host; Firefox launches it when you arm a tab.

Platform: GNU/Linux only.
Source and full documentation: https://github.com/simddev/FetchGate