Corrections to Algebraic Topology --- last updated June 2, 2021.

Below is a cumulative list of corrections, clarifications, and comments for the various printings of the book. The list can also be downloaded in pdf format, with a few more details in some cases. Most of these corrections have been incorporated into later printings. Undoubtedly more errors remain to be discovered. If you find any, please send them to me for inclusion in this list and to correct future printings and the online version of the book.