PlanetMath is a virtual community which aims to help make mathematical knowledge more accessible. PlanetMath's content is created collaboratively: the main feature is the mathematics encyclopedia with entries written and reviewed by members (subject index, alphabetical index).

The entries are contributed under the terms of the Creative Commons By/Share-Alike License in order to preserve the rights of authors, readers and other content creators in a sensible way. Entries are written in LaTeX, the lingua franca of the worldwide mathematical community. Articles are then rendered for presentation on the web using LaTeXML, and links between them are added using NNexus.

As of 2018, source files are editable via planetmath's repositories on Github: acceptable pull requests will be merged by one of our Editors.

Along with this change to the way editing works, the legacy forums have been decommissioned, and we have created Gitter discussion channels for each mathematics subject category, in order to facilitate real-time discussion.

The PlanetMath.org website is hosted by the University of Waterloo Faculty of Mathematics. PlanetMath.org, Ltd., is a 501(c)3 nonprofit, incorporated in Alexandria, Virginia, USA.