Free, open-source alternatives to Todoist

Todoist is a to-do list that syncs between your devices. You add tasks in plain language, such as "send report every Friday", and it turns that into a due date or a recurring task, then groups everything into projects with a calendar view and shared spaces for teams. It is not open source, and it works through a Todoist account.

Mindwtr is built around Getting Things Done: tasks go into an inbox first, get sorted into projects, and come back in a weekly review, all offline without an account. Super Productivity is a to-do list that also plans your day, with timeboxing, time tracking, focus sessions and imports from Jira, GitHub and other issue trackers. Neither copies Todoist's natural-language input exactly, but both cover the job of keeping and planning a task list.