JWT Token
Definition
A compact, URL-safe token format used for securely transmitting information between parties as a JSON object, commonly used for authentication and authorization in web applications.
JSON Web Tokens consist of three parts separated by dots: a header specifying the token type and signing algorithm, a payload containing claims about the user or session, and a signature that verifies the token has not been tampered with. The header and payload are Base64URL-encoded JSON objects, making JWTs compact enough to be transmitted in HTTP headers, URL parameters, or cookies.
JWTs are widely used in modern authentication flows. After a user logs in, the server generates a JWT containing the user's identity and permissions, which the client includes in subsequent API requests. Because the server can verify the token's signature without querying a database, JWTs enable stateless authentication that scales well across distributed systems and microservices architectures.
Security best practices for JWTs include using strong signing algorithms like RS256 or ES256 rather than HS256, setting short expiration times and using refresh tokens for extended sessions, never storing sensitive data in the payload since it is only encoded and not encrypted, and transmitting tokens exclusively over HTTPS. Common vulnerabilities include the none algorithm attack, where attackers forge tokens by specifying no signing algorithm, and token hijacking through cross-site scripting.
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Related Terms
JWT (JSON Web Token)
techA compact, URL-safe token format used for securely transmitting information between parties as a JSON object, commonly used for authentication.
Encryption
techThe process of converting readable data (plaintext) into an unreadable format (ciphertext) using an algorithm and key, protecting it from unauthorized access.
Hash
techA fixed-length string of characters generated from input data by a hash function, used for data integrity verification, password storage, and digital signatures.
SSL/TLS (Secure Sockets Layer / Transport Layer Security)
techCryptographic protocols that provide secure communication over computer networks, encrypting data between a web server and browser.
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