JSON Web Tokens (JWT): What They Are and How to Use Them

JWT Authentication flow

Introduction

Before the advent of JSON Web Tokens (JWT), web authentication relied on cookies or sessions to authenticate users to web applications. These methods were good but had some drawbacks like scalability, storage limitations, and difficulty in integrating with third-party services. JWT solved these issues by providing a simple, secure, and flexible way to authenticate users in web applications.

What is JWT?

JSON Web Token (JWT) is a compact and self-contained method for securely transmitting information between parties as a JSON object. It is a standardized way to represent claims that are encoded as a JSON object and digitally signed using cryptographic algorithms. JWT consists of three parts: header, payload, and signature.

JWT structure

Header

The header contains metadata about the token such as the type of token and the cryptographic algorithm used to sign it. The header is encoded in Base64Url format.

{
  "alg": "HS256",
  "typ": "JWT"
}

Payload