LinkCage

LinkCage opens links you don't trust inside a throwaway, isolated browser - on your own computer - so nothing dangerous touches your real browser.

REQUIREMENTS (read before installing) This add-on is one part of a three-part tool. It needs:

• Docker Desktop, installed and running, and
• The free, open-source LinkCage companion host (one-time install). The add-on is only the trigger. Without Docker and the host it cannot launch a sandbox. Setup: https://linkcage.app

HOW IT WORKS Right-click an untrusted link and choose "Open in LinkCage." The URL is handed, via native messaging, to the local companion host, which spins up a disposable Chromium browser inside an isolated Docker container. Malicious content stays in that container - never reaching Firefox, your files, or your credentials. Close it and the container is destroyed (RAM-only).

Before the page loads, the host checks the link against URLhaus and Google Safe Browsing and shows a SAFE / SUSPICIOUS / MALICIOUS splash.

PRIVACY

• No LinkCage cloud service; the add-on sends nothing to us.
• The add-on transmits the clicked URL only to the local companion host, over native messaging.
• The host performs the reputation lookup directly against URLhaus and Google Safe Browsing. In-sandbox browsing is not logged or transmitted.
• Open-source and auditable.

WHAT IT IS NOT Not antivirus. It does not monitor or filter normal Firefox browsing. It isolates only the links you choose to cage.

Source & install: https://linkcage.app