What Exactly is a JWT and How Does it Work?

A JSON Web Token (JWT) is a standard for securely transmitting information between a client and server as a JSON object. JWTs are primarily used for authentication and authorization in web applications, being compact enough to be transmitted easily. A JWT consists of three parts: a header, a payload, and a signature, each separated by periods. The header contains metadata like the token type and hashing algorithm. The payload holds the data, often user information or permissions, also known as claims. The signature ensures the token's integrity, combining the header, payload, and a secret key. JWTs are more secure due to public/private key signing, and are compact, scalable, and portable. They are stateless, reducing database lookups and improving performance. Common mistakes include storing sensitive data in the payload and not using HTTPS. Best practices include short expiration times and secure storage, and using HTTPS. By following these best practices, developers can effectively utilize JWTs for authentication, ensuring application security and efficiency.