Trello is a web-based, kanban-style, list-making application and is developed by Trello Enterprise, a subsidiary of Atlassian. Created in 2011 by Fog Creek Software, it was spun out to form the basis of a separate company in New York City in 2014 and sold to Atlassian in January 2024.

On the surface, Planner and Trello are quite similar. Both are online Kanban tools designed to streamline task and project management. Both belong to extensive product suites of Microsoft and Atlassian respectively.