It operates a freemium business model, as well as being cross-subsidized by other Fog Creek Software products. A basic service is provided free of charge, though a Business Class paid-for service was launched in 2013.
Trello was released at a TechCrunch event by Fog Creek founder Joel Spolsky.Wired magazine named the application in September 2011 one of "The 7 Coolest Startups You Haven’t Heard of Yet".Lifehacker said "it makes project collaboration simple and kind of enjoyable".
In July 2012, the site surpassed 500,000 users. They claimed in December 2012 that it had surpassed 1,000,000 and in May 7, 2014, they claimed the number to be four million. On September 18, 2014 Trello reached over five million users. As of 14 October 2015, it claims to have 10 million users.
Trello uses the kanban paradigm for managing projects, originally popularized by Toyota in the 1980s for supply chain management. Projects are represented by boards, which contain lists (corresponding to task lists). Lists contain cards (corresponding to tasks). Cards are supposed to progress from one list to the next (via drag-and-drop), for instance mirroring the flow of a feature from idea to implementation. Users can be assigned to cards. Users and boards can be grouped into organizations.
It supports iPhone, Android and Windows 8 mobile platforms, however, its website has been designed to be accessible in most mobile web browsers. An iPad application was released on March 12, 2013. It added support for an unlimited number of tags, in the form of colored labels that can be renamed and new ones created, starting November 21, 2014. Cards accept comments, attachments, votes, due dates and checklists. Trello has an API. Users may organize projects through the utilization of boards, lists and cards, which form a bespoke data hierarchy that facilitates effective management of projects, jobs and tasks.
Trello has a variety of work and personal uses including real estate management, software project management, school bulletin boards, lesson planning, and law office case management. A rich API as well as email-in capability enables integration with enterprise systems, or with cloud-based integration services like IFTTT and Zapier.