Middleware for API routes in NextJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is middleware in Next.js API routes?

Middleware is a function that runs before the main API route handler. It can modify the request or response, or stop the request from continuing.

beginner

How do you apply middleware to a Next.js API route?

You create a middleware function and call it inside your API route handler before your main logic. You can also compose multiple middleware functions.

beginner

What is a common use case for middleware in API routes?

Middleware is often used for tasks like checking user authentication, validating data, or logging requests before the main API logic runs.

intermediate

How can middleware stop an API request from continuing?

Middleware can send a response early (like an error or redirect) and not call the next handler, which stops the request from reaching the main API logic.

intermediate

Why is middleware helpful for code reuse in Next.js API routes?

Middleware lets you write common logic once and use it in many API routes, so you don’t repeat code and keep your routes clean.

What does middleware in Next.js API routes do?

A Runs before the main API handler to process requests

B Runs after the API response is sent

C Only handles errors in API routes

D Replaces the API route handler completely

Middleware runs before the main API handler to modify or check requests.

How can middleware stop an API request from continuing?

A By calling the next handler

B By throwing an error without response

C By modifying the request body

D By sending a response early and not calling next

Middleware can send a response early and skip calling the next handler to stop the request.

Which is NOT a typical use of middleware in Next.js API routes?

A Authentication checks

B Rendering React components

C Logging requests

D Data validation

Rendering React components is done in pages or components, not middleware in API routes.

How do you add middleware to a Next.js API route?

A By importing and calling it inside the API handler

B By adding it to next.config.js

C By naming the file middleware.js

D By using a special middleware keyword in the route

Middleware is added by importing and calling it inside the API route handler.

Why use middleware for common logic in API routes?

A To slow down API responses

B To repeat code in every route

C To keep routes clean and reuse code

D To avoid using API routes

Middleware helps reuse common logic and keeps API routes clean.

Explain how middleware works in Next.js API routes and give an example use case.

Think about what happens before your API code runs.

Describe how you would add middleware to a Next.js API route and why it is useful.

Focus on the steps and benefits.