Nuclei is an open-source cybersecurity tool designed for fast, automated vulnerability scanning. Developed by ProjectDiscovery, Nuclei uses customizable templates to identify security issues in web applications, APIs, and network infrastructure. Its flexible architecture allows security professionals to write or modify templates for specific vulnerabilities, making it adaptable to evolving threats. Nuclei is widely used in penetration testing, bug bounty programs, and continuous security monitoring. Its speed, scalability, and community-driven template repository make it a popular choice for both individual researchers and organizations aiming to automate their security assessments. Nuclei integrates easily with other tools and CI/CD pipelines, enhancing overall security workflows.