Cookies play a crucial role in web development, serving purposes like user authentication, session management, and tracking user preferences. In Next.js, managing cookies involves various methods, each with unique considerations. For instance, in the Pages Router, cookies can be set in getServerSideProps, allowing HttpOnly cookies that aren't accessible via JavaScript. API Routes offer a similar approach, but special attention is needed when setting multiple cookies simultaneously to avoid overwriting. The App Router introduces a cookies function for easier cookie management, though it has limitations. Middleware in Next.js can modify and set cookies on responses, although forwarding modified cookies requires a workaround involving headers. Server Actions offer another way to manage cookies, enabling server-side operations triggered by actions like form submissions. Additionally, client-side cookies can be managed using libraries like react-cookie, but developers are encouraged to consider alternatives like localStorage for storing non-sensitive data, given it doesn't send data with every request and provides more storage capacity.