HabitLab is a free Chrome add-on developed by the Stanford HCI Research Group. It is an open-source research project aimed at helping users reduce their time spent online and build better habits.

The add-on offers a variety of tools, including news feed blockers, comment hiders, and more. When you visit a site, HabitLab intelligently selects an intervention to help you reduce your time on the site. These interventions can include hiding your news feed, hiding comments, pausing videos, showing notifications if you've been on a site for too long, and more. If you don't like a particular intervention, you have the option to disable it.

HabitLab learns from your browsing history and past effectiveness to determine which interventions work best for you. This data is recorded for research purposes.

Overall, HabitLab is a useful tool for those looking to reduce their time online and develop healthier online habits. It provides a customizable and effective way to achieve this goal.