Perception is a Python library for perceptual image and video hashing, developed by Thorn. It provides a unified interface for multiple hashing algorithms (e.g., pHash, dHash, PDQ, TMK), approximate nearest neighbor search via FAISS with graph-based clustering, and a benchmarking framework for evaluating hasher robustness under various transformations. The library is designed for production use cases like near-duplicate detection, content matching, and CSAM detection via integration with Thorn's Safer service. The codebase demonstrates strong engineering practices: clean abstractions, Cython acceleration, optional dependency management, and extensive test coverage. While primarily an application/library, it includes research-oriented benchmarking pipelines and evaluation datasets, making it a hybrid of production tooling and research infrastructure.