Iridium Browser is a free and open source web browser with a focus on privacy and security. The Iridium project takes the Chromium code base (the open source component of Google Chrome) but modifies it to enhance security and require user consent before storing or transmitting any user data. For example, by default, Iridium always sends a Do-Not-Track header, blocks third-party cookies, clears site data on exit, disables form autofill, does not save passwords, and disables Network/DNS prediction. The full list of changes can be found under the Manifest section on the Iridium website. Users can opt-in to features that store or transmit their data on a case by case basis, deciding for themselves how they wish their data to be treated. Iridium Browser is available for Windows, macOS, and Linux. Source code is available on GitHub, with most components available under the BSD license.