  The accelerated growth rate of repository entries in crystallographic
databases makes it arduous to identify and classify their prototype structures.
The open-source AFLOW-XtalFinder package was developed to solve this problem.
It symbolically maps structures into standard designations following the AFLOW
Prototype Encyclopedia and calculates the internal degrees of freedom
consistent with the International Tables for Crystallography. To ensure
uniqueness, structures are analyzed and compared via symmetry, local atomic
geometries, and crystal mapping techniques, simultaneously grouping them by
similarity. The software i. distinguishes distinct crystal prototypes and atom
decorations, ii. determines equivalent spin configurations, iii. reveals
compounds with similar properties, and iv. guides the discovery of unexplored
materials. The operations are accessible through a Python module ready for
workflows, and through command line syntax. All the 4+ million compounds in the
AFLOW.org repositories are mapped to their ideal prototype, allowing users to
search database entries via symbolic structure-type. Furthermore, 15,000 unique
structures - sorted by prevalence - are extracted from the AFLOW-ICSD catalog
to serve as future prototypes in the Encyclopedia.
