Momentum extension for Chrome replaces your new tab page with a calming photo, a greeting and a daily focus prompt. That works as a gentle nudge, but it does not stop you from opening distracting sites. If blocking or limiting time on specific websites is your actual goal, a dedicated focus extension does more of the work.
Why people look for a Momentum alternative
Momentum google chrome extension is designed around motivation: a new tab dashboard with a photo, weather, to-do list and a daily question. It does not block or limit any website, so if your new tab habit is the problem, replacing the tab's look will not stop you from typing in a distracting URL directly.
BlockSite for scheduled focus time
BlockSite is a freemium extension that blocks distracting sites outright and lets you schedule focus time windows, such as blocking social media during work hours. It addresses the behavior Momentum only decorates around, making it a better fit if distraction, not new tab aesthetics, is the real issue.
StayFocusd for time limits
StayFocusd is a free extension that limits the total time you can spend on time-wasting websites each day, rather than blocking them outright. It suits people who want to allow brief checks of a site without losing the whole afternoon, which is a different model from Momentum's passive new tab approach.