The promise of the internet was open knowledge and connection; the reality includes manipulation, abuse and mistrust. This book confronts that gap with a practice-oriented guide to designing, analysing and governing safer digital ecosystems. Authored by experts across academia, industry and government, it is organized around three pillars – (a) safety by design and provenance, (b) threat detection and analysis and (c) response and mitigation – to embed safeguards, surface emerging harms and execute effective incident response at scale. Chapters pair empirical studies with deployable techniques, from evaluation metrics and audits to governance and enforcement frameworks, situating technical advances within real-world constraints of cost, scale, privacy, equity and culture. This resource offers researchers, policymakers, platform builders, educators and civil society a clear map of today’s landscape as well as a pragmatic agenda for what can and should come next: transparent provenance, robust measurement and accountable interventions that earn user trust.