Typing # while entering a new task brings up the list of projects (and sub-projects) to assign the task to. Type in any letters of the project name to filter the list to a subset of projects that have those letters in them.

Anyone can be invited to collaborate on tasks and projects. Users can work alongside five people for free and 25 via the paid version. Collaboration includes the ability to assign tasks, comment on tasks, and receive instant updates.

By clicking on a task and then selecting “schedule,” a dialog box will pop up with shortcuts like "today," "tomorrow," or "postpone until tomorrow." A date can still be entered manually.

Todoist's web and desktop interfaces have a 2-column layout. The right column has all tasks organized in nested lists with color codes and information such as what people are assigned to each task and which project the task is part of. The left column offers ways of accessing various groups of tasks – tasks that have to be completed within a certain timeframe, tasks that are a part of a certain project or have certain labels attached to them, etc. The left column also contains filters that allow even more advanced ways of finding a group of tasks.

The mobile interface follows a similar design philosophy, but gives each column a separate view.