Authentication is one of the ways of securing your applications (the communication between the client and server) and one effective method is 

, which ensures users can securely access protected resources

This guide explains how token authentication works, focusing on 

This is a method where users authenticate once and receive a token, which is then sent with every request to verify identity. Unlike session-based authentication, which relies on storing session data on the server, tokens allow for 

There are different kind of authentication methods, which are:

 - Single Sign-On via third parties like Google, Microsoft, etc.

 Hardware devices like YubiKeys, smart cards

 (email & password) on the client side, by filling in a form.

The client sends it to the server, which is then validated

 securely (e.g., in memory or HTTP-only cookies).

 in the request header for protected routes.

One of the widely used methods for securing API authentication. They provide a stateless way of authenticating users, allowing applications to verify identity without storing session data on the server.

 is a compact, URL-safe token format that encodes JSON objects to form a secure way in which data is transferred through two parties. It mainly consists of three parts:

 - Specifies token type and signing algorithm that is used.

 - Contains claims (usually data about the user or entity). like user ID, role, and expiration time.

 - Ensures token integrity using a secret key. A signature is created using the algorithm specified in the header to sign a combination of the encoded header, the encoded payload and a secret. The secret helps us verify that the token hasn’t been tampered with and should be kept somewhere safe (you can use env variables)

NOTE: You should not always include sensitive data in the payload, since it isn't secured by default unless there is additional encryption.

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Authentication flow: in-depth explanation

Validate and sanitize input (e.g., check email format, ensure fields aren’t empty, enforce strong passwords).

Package the data into a JSON object and send it to the signup endpoint.

Hash and salt the password using a library like 

Check for duplicate users (if needed) and save the user details in the database.

NB: Enhance the authentication flow by redirecting users directly to the app after signup instead of the login page. Since we already have the user’s credentials, we can issue an access token upon signup, just like during login.

Collect user credentials and validate input (e.g., check email format, ensure fields aren’t empty).

Package the data into a JSON object and send it to the login endpoint.

Compare the stored hashed password with the one provided by the user.

Using a JWT library, generate two tokens:

Short-lived (expires in minutes or hours).

Contains essential data like user ID, roles, and permissions.

Used to generate new access tokens when the current one expires.

Sent back to the client as a JSON response.

Stored in memory using state, context, or variables (e.g., in React).

Used in the Authorization header for all protected requests.

NB: Avoid storing access tokens in local storage due to XSS risks. Keeping them in memory is safer unless the application has JavaScript injection vulnerabilities.

Automatically included in requests to the server.

Helps mitigate XSS attacks and, with proper security settings, can prevent CSRF attacks.

NB: Configuring SameSite cookies or CSRF tokens can further enhance your security.

 is primarily used for authenticating requests. It is short-lived, typically lasting from a few minutes to several hours. With every request, the access token is sent in the 

 to verify the user's identity and permissions. Since it expires quickly, it has a lower security risk. Access tokens generally contain data such as the 

 is used to generate new access tokens when the current one expires. It has a much longer lifespan, lasting from 

 dedicated to refreshing tokens. Unlike access tokens, refresh tokens are typically stored in an 

 for added security. They contain minimal information, such as the 

, but pose a higher security risk if exposed, as they can be used to obtain new access tokens.

The client includes the access token in the Authorization header of each request.

The server verifies the token, checks its expiry, decodes it, validates permissions, and then processes the request.

When the access token expires, the client requests a new one using the refresh token.

The server retrieves the refresh token from the HTTP-only cookie, verifies it, and issues a new access token.

Optionally, the old refresh token can be blacklisted to prevent reuse.

The client stores the new access token and continues making requests.

NB: Passport.js provides a robust authentication library that simplifies this process across various frameworks.

 Detects token expiry errors on the client, requests a new token, and retry the failed request automatically—seamlessly handling it in the background.

 Track token expiry on the client and refresh it before it expires. However, this method may introduce unnecessary requests, impacting performance.

This approach ensures a smooth user experience without requiring users to manually re-authenticate frequently.

Below are some of the practices in points you can consider:

 to encrypt traffic and prevent token interception. 

 and avoid hardcoding them in the codebase. 

 by scope and role-based access control (RBAC)

This guide gives you a heads-up for how token-based authentication works and makes it easy to understand while implementing it in any of your favorite languages.

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Token-Based Authentication Guide

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