PermPAL, the Permutation Pattern Avoidance Library, is a research database of algorithmically derived theorems about permutation classes. It contains 24,454 classes for which the Combinatorial Exploration framework has automatically found rigorously verified combinatorial specifications. These specifications can support further results, including generating functions, counting sequences, polynomial-time counting algorithms, and random sampling procedures.

The library covers classes previously enumerated by other methods as well as classes not previously enumerated. Its notable results include most principal classes of length four, all symmetry classes avoiding two or three patterns of length four, and classes connected to work on the permutation 1324 and Schubert varieties. The site also provides search, random browsing, and examples to help users explore its collection.

PermPAL is supported by open-source software: the comb_spec_searcher Python framework and the tilings codebase, which applies the framework to permutation patterns. The project welcomes questions, comments, bug reports, and feature suggestions, and asks researchers who use the database to consider citing its associated work.