The best alternative to Microsoft Planner is Taiga.io, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to Microsoft Planner and 14 are so hopefully you can find a suitable replacement. Other interesting alternatives to Microsoft Planner are Org mode, Lunatask, Things and Zenkit.
Microsoft Planner alternatives are mainly Project Management Tools, but if you're looking for
Task Management Tools or Todo List Managers you can filter on that. Other popular filters include
Open Source,
Free and
Mac. You can also filter by region, for example
EU-based alternatives if you prefer software developed in the European Union. These are just examples - use the filter bar below to find more specific alternatives to Microsoft Planner.