Why Modern Apps Use Refresh Tokens (and How They Work)

Introduction

When we log in to an application, we don’t want to keep entering our username and password again and again. To solve this, modern authentication systems use Access Tokens and Refresh Tokens. These two tokens work together to provide security and a smooth user experience.

1. What is an Access Token?

An Access Token is a short‑lived credential given to a user after successful login.

• Usually in JWT (JSON Web Token) format.

• Contains user details such as:

  • User ID

  • Roles & permissions

  • Expiration time

• Sent with every request to the server (e.g., Authorization: Bearer <token>).

💡 Example: Access tokens often expire in 15 minutes – 1 hour.

This ensures better security, because even if someone steals it, they can’t use it for long.

Problem: Once it expires, the user is forced to log in again. That’s frustrating for someone working long hours.

2. What is a Refresh Token?

A Refresh Token solves this problem.

• It is a long‑lived token (days, weeks, or months).

• Stored securely on the server side or encrypted in the client.

• Its job: request a new access token when the old one expires.

👉 Instead of asking the user to log in again, the application uses the refresh token behind the scenes.

3. How Do They Work Together?

Here’s the flow:

1. Login: User logs in → Server issues Access Token + Refresh Token.

2. Use App: User sends Access Token with each request → Server verifies and allows access.

3. Expiry: Access Token expires after a short time.

4. Refresh: Application silently calls /auth/refresh with Refresh Token.

5. New Token: Server verifies refresh token → issues a new Access Token.

6. Continue: User keeps working without being forced to log in again.

4. Why Both Tokens?

• Access Token = Short‑lived → Safer if stolen.

• Refresh Token = Long‑lived → Maintains session without re‑login.

• Combined → Balance between security and convenience.

5. Benefits

• Smooth user experience (no repeated logins).

• Stronger security (short lifespan reduces token misuse).

• Revocable (refresh tokens can be blocked if suspicious activity is detected).

📌 In Short

• Access Token = “A temporary pass to access resources.”

• Refresh Token = “A secret key to get new passes without logging in again.”

Together, they form the backbone of secure authentication systems used by Google, Facebook, and almost every modern app today.

I would like to thanks my mentor Hitesh Choudhary Hitesh Choudhary for explaining and that explaination forced me to write this article

Thankyou

#authentication, #security, #jwt, #webdev, #beginners