The nLab is a wiki for research-level notes, expositions and collaborative work, including original research, in mathematics, physics, and philosophy, with a focus on methods from category theory and homotopy theory. The nLab espouses the "n-point of view" (a deliberate pun on Wikipedia's "neutral point of view") that category theory and particularly higher n-category theory provide a useful unifying viewpoint for mathematics, physics and philosophy.
The nLab was originally conceived to provide a repository for ideas (and even new research) generated in the comments on posts at the n-Category Café, a group blog run (at the time) by John Baez, David Corfield and Urs Schreiber. It was set up on November 28, 2008 by Schreiber using the Instiki software provided, maintained and installed by Jacques Distler. Eventually the nLab developed into an independent project which has since grown to include whole research projects and encyclopedic material. Andrew Stacey is the current system administrator who runs the technical side of the nLab. The nLab has an informal steering committee, which "doesn't run the nLab", but exists in order to resolve issues that would cause the whole project to run into trouble.
The nLab is associated with the nForum, an online discussion forum (also run and maintained by Stacey) for announcement and discussion of nLab edits (the analog of Wikipedia's "talk" pages) as well as for general discussion of the topics covered in the nLab. The preferred way of contacting the nLab steering committee is to post on the nForum. An experimental sub-project of the nLab is the Publications of the nLab, intended as a journal for refereed research articles that are published online and cross-hyperlinked with the main wiki.
The nLab is listed on MathOverflow as a standard online mathematics reference to check before asking questions. Many questions link to the nLab for background material. The nLab is one of two wikis mentioned by the mathematical physicist John Baez in his review of math blogs for the American Mathematical Society.
- nPOV in nLab
- Steering committee in nLab meta
-  in nLab meta
- MathOverflow, 1.0 'How to ask' page. Archived on 2013-06-04.
- MathOverflow, Results for a search for 'nlab'. As of 2014-02-28 there are over 500 results.
- John C. Baez, "Math Blogs", Notices of the American Mathematical Society, March 2010