Poster: Legal Imprints as an Identity Anchor for Web Measurement

Current measurements of Web infrastructure largely lack visibility into the commercial entities, or Digital Service Providers (DSPs), that operate individual domains. We present the first large-scale mapping of domains to their corresponding operating companies. Leveraging the imprint (Impressum) mandated by German and European law for commercial websites, our pipeline crawls 8.2 million .de domains, extracts imprint fields using deterministic patterns alongside constrained local-LLM extraction, and verifies each record against the German commercial register (Handelsregister). Achieving 99.4 % precision and 96.9 % recall, this process yields 707 426 verified domain-to-operator mappings. We leverage this dataset to re-evaluate web centralization at the DSP rather than the domain level, and to relate hosting jurisdictions to corporate legal forms and firm ages. Ongoing work ports the pipeline to France and Spain. We plan to release the dataset under GDPR-compliant terms, alongside our crawler and analysis code.