TeXShop is a front end to TeX on the Macintosh. It provides a source editor, a preview window to display pdf files, a second preview window to display html files live on the internet, and windows to display console messages and log files. It supports a large number of typesetting engines like TeX and LaTeX, XeTeX, LuaTeX, ConTeXt, and many others. The program is released under the GNU General Public License, Version 2. The main author is Richard Koch, koch@uoregon.edu, with supporting contributions from many other people. Consult the program web site, https://pages.uoregon.edu/koch/texshop/texshop.html, for full source code, an extensive Changes document, and other information. The current version, 5.21, was released on October 20, 2023.