H4cker is a large open-source collection of cybersecurity references, scripts, tools, code, labs, and training material curated by security researcher Omar Santos. The repository serves as a practical companion to books, courses, and live training while also functioning as a broad standalone knowledge base for people studying or working in cybersecurity.

Its material spans offensive and defensive security, application security, cloud and container security, infrastructure and networking, cryptography, governance and compliance, hardware security, AI security, incident response, and hands-on lab building. Separate sections also organize certification resources, cheat sheets, tools, projects, and other reference material.

Rather than focusing on one security product, H4cker acts as a structured learning and reference hub. It is useful for security students, practitioners, certification candidates, instructors, and researchers who want a single repository containing practical examples and curated paths into many different cybersecurity domains.