This is a major release focused on enhancements. Most notably, parallel processing is now turned on by default for "trackpy.batch" and "trackpy.locate_brightfield_ring", resulting in a large performance increase for many users. Another minor speedup changes the way in which particle numbers are generated, which may cause issues with reproducibility in some existing workflows (see "API Changes" below). Note that Python 2 reached end-of-life in 2020, and it is no longer officially supported by trackpy. Also, trackpy dropped support for older NumPy, Scipy and Pandas. The current minimum requirements are: python>=3.6 numpy>=1.14 scipy>=1.1 pandas>=0.22. See the "What's new in the package" page in the documentation for a full list of changes.