This guide explains best practices for keeping sensitive information, or "secrets," secure in modern applications. The foundation of secrets management is understanding what constitutes a secret and how it can be exploited if exposed. Secrets include API keys, database credentials, SSH and encryption keys, and passwords. Preventing secrets from being committed to repositories is crucial, and tools like pre-commit scanning and version control security features can help catch exposed secrets before they reach the repository. Environment management is also key, using environment variables to define and load sensitive values across local development and production systems. As applications grow in complexity, modern secrets managers offer advanced features like automated rotation, fine-grained access control, and dynamic secrets. Scaling secrets management requires minimizing hardcoded secrets, automating rotation, auditing access, and integrating with infrastructure-native solutions. Centralized tools can simplify the process of managing secrets across multiple environments and stakeholders, ensuring compliance with standards like SOC 2 and GDPR. Effective secrets management costs less than a breach but requires a comprehensive approach that evolves with your organization.