JSON Web Tokens (JWT) are an open standard for securely sharing JSON data between parties and are widely adopted in modern web development for authentication and authorization workflows. JWTs consist of three parts: a header, payload, and signature. To ensure the safety of users and apps, it's crucial to validate JWTs by parsing them, verifying their signatures, checking expiration times, and ensuring they were issued by trusted parties. Libraries such as jose (Node), jwt-go (Golang), PyJWT (Python), JWT (Ruby), PHP-JWT (PHP), jose.4.j (Java), and IdentityModel Extensions for .NET can be used to validate JWTs. Best practices include keeping secret keys safe, always validating JWTs, using secure libraries, and employing strong encryption algorithms.