This Zenodo deposit contains the supplementary materials and reproduction package for the paper: “Black-Box Mutation Testing of Web APIs”. The artifact provides: HttpMutator: a black-box mutation testing tool for web APIs that generates faulty yet realistic variants of HTTP responses (status codes, headers, and JSON payloads). httpmutator-benchmark: a benchmark and the authoritative reproduction guide (the “start here” instructions) for running the experiments reported in the paper. httpmutator-exp: experiment harnesses / scripts used to integrate HttpMutator with API testing tools and to collect results. Repository layout (inside the archive) httpmutator/ — core tool and library httpmutator-benchmark/ — benchmark + reproduction guide httpmutator-exp/ — experiment harnesses, integrations, and scripts Quick reproduction Please start from the reproduction guide: httpmutator-benchmark/README.md (authoritative guide) It describes prerequisites, environment setup (e.g., Java/Maven, Python, Docker), and step-by-step commands to reproduce the main experimental results. Expected outputs The reproduction guide specifies where outputs are stored (e.g., logs, generated mutants, and aggregated result tables) and how to map them to the corresponding tables/figures in the paper.