Next.js Basic Authentication

Common errors

• Error: API resolved without sending a response for /protected, this may result in stalled requests.

  cause The `basicAuthCheck(req, res)` function handles the response for unauthenticated users (sending a 401). If the page's `getServerSideProps` (or equivalent) doesn't explicitly return `props` after a successful authentication, Next.js might warn about an unhandled response.
  fix Always return an object with a `props` key from `getServerSideProps` after the `basicAuthCheck` has successfully passed, e.g., `return { props: {} };`.

• 401 Unauthorized

  cause This is the expected response when basic authentication fails, either due to incorrect username/password or missing credentials in the request header.
  fix Ensure correct 'Authorization: Basic <base64-encoded-credentials>' header is sent with the request, or input correct credentials when prompted by the browser.

• TypeError: Cannot read property 'url' of undefined

  cause This specific error (or similar related to `req` or `res` properties) might occur if `basicAuthCheck` is called outside of a server-side context where `req` and `res` objects are not available, or if incorrect arguments are passed.
  fix Ensure `basicAuthCheck` is only ever called inside `getServerSideProps` (Pages Router) or a similar server-side function/middleware with the `req` and `res` objects correctly destructured from the context (`ctx`).

Warnings

• breaking This package is designed for the Next.js Pages Router and relies on `getServerSideProps`. It does not directly support the new App Router's server components or middleware architecture in the same way. Adapting it for the App Router would require significant manual changes or a different approach.
  Fix: For App Router, consider implementing basic auth via Next.js Middleware (e.g., `nextjs-basic-auth-middleware`) or server-side checks within Route Handlers, or using a more comprehensive auth solution like NextAuth.js.
• gotcha Protecting a route with `nextjs-basic-auth` requires that the page opts out of Next.js's Static Site Generation (SSG). Pages using this library *must* use `getServerSideProps` or a similar server-side rendering mechanism, as the authentication check needs access to the `req` and `res` objects at runtime.
  Fix: Ensure the protected page explicitly uses `export async function getServerSideProps(ctx) { ... }` (Pages Router) or a server-side rendering strategy (App Router) which prevents static pre-rendering.
• gotcha Storing sensitive credentials like user passwords directly in source code, even if hashed, is a security risk. The `users` array should ideally be populated from secure environment variables or a database, especially for production environments.
  Fix: Utilize environment variables (e.g., `process.env.ADMIN_PASSWORD`) to store passwords for non-development use, or fetch user credentials from a secure backend database or API.
• deprecated The package has not seen updates in over 5 years. While it may still function for its specific use case, it does not leverage newer Next.js features like Middleware for authentication, which is generally a more recommended approach for global or group-based route protection in modern Next.js applications.
  Fix: Consider migrating to Next.js Middleware for authentication (e.g., `nextjs-basic-auth-middleware`) or a full-fledged authentication library like NextAuth.js for more robust and maintainable solutions, especially for Next.js versions 12 and above.

Install

• npm install nextjs-basic-auth npm
• yarn add nextjs-basic-auth yarn
• pnpm add nextjs-basic-auth pnpm

Imports

• initializeBasicAuth
  wrong:

  const initializeBasicAuth = require('nextjs-basic-auth')

  correct:

  import initializeBasicAuth from 'nextjs-basic-auth'

  The package uses ES Modules by default. While Node.js can sometimes interop, explicit ESM import is preferred. CommonJS `require` might lead to issues or incorrect imports depending on project configuration.

Quickstart

Demonstrates initializing basic authentication with a list of users and applying it to a Next.js page using `getServerSideProps` to protect the route.

import initializeBasicAuth from 'nextjs-basic-auth';

const users = [
  { user: 'user1', password: 'toocool' },
  { user: 'admin', password: process.env.ADMIN_PASSWORD ?? 'password' }, // Use env vars for production!
];

// Initialize the basic auth checker once globally or per module
const basicAuthCheck = initializeBasicAuth({
  users: users
});

// In your Next.js page file (e.g., pages/protected.js or app/protected/page.js for Pages Router or App Router with getServerSideProps emulation)
export async function getServerSideProps(ctx) {
  const { req, res } = ctx;

  // Await the auth check. If authentication fails, it will send a 401 response and prompt the user.
  await basicAuthCheck(req, res);

  // If authentication passes, proceed with rendering the page
  return {
    props: {},
  };
}

// If using the App Router, this pattern is less direct and would typically involve server components or middleware.
// This example is primarily for the Pages Router where getServerSideProps is common.