How to verify JWTs in a Next.js App Router app

JWT verification is crucial in ensuring that authenticated user information is accurately processed and secure within applications, particularly when using frameworks like Next.js. This process involves verifying the JWT signature, time-based claims, issuer, and audience to maintain security, with the choice of verification method and library being essential for proper implementation. In Next.js, JWT verification can occur in middleware, server components, route handlers, or server actions, depending on the application's architecture and needs. Middleware runs on Edge, requiring libraries like jose that are compatible with the Web Crypto API, while traditional Node environments can use libraries like jsonwebtoken. Choosing between symmetric (HS256) and asymmetric (RS256) algorithms depends on the trust boundaries and whether tokens are shared across multiple services or third-party providers. Proper placement of verification within the application and the use of secure storage methods, such as httpOnly cookies, are emphasized to avoid common security pitfalls. The article further suggests using tools like WorkOS AuthKit for handling broader authentication tasks, while developers maintain control over JWT verification within their code.