What really is the difference between session and token based authentication
Tags: authentication, webdev, backend, javascript
Published: 2019-01-13 00:05:04

---
title: What really is the difference between session and token based authentication
published: true
description: A simple explanatory article about the difference in authentication techniques
tags: authentication, web dev, backend, javascript
---
A friend who is just getting into using Nodejs for backend development asked me to explain the difference between using session and jwt. So I thought I’d write this for any other person trying to understand what it means when you hear other developers talk about sessions and token based authentication.

## Quick Introduction
Firstly, let’s talk about the HTTP (HyperText Transfer Protocol). From a quick Google search we get that:

> HTTP is the underlying protocol used by the World Wide Web and this protocol defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands.

From the above definition, we can tell that HTTP is what enables communication between a client (frontend) and a server (backend). HTTP is stateless so each request made is totally unaware of any action taken previously. Say for example we just logged into our twitter account and we navigate to our settings page, with the default HTTP behavior, we would be required to log back in again because the server has no idea that we just logged in but with session and token authentication we can tell the server that we are already logged in and we have should be granted access to that page.

## What is session based authentication?
Session based authentication is one in which the user state is stored on the server’s memory. When using a session based auth system, the server creates and stores the session data in the server memory when the user logs in and then stores the session Id in a cookie on the user browser.
The session Id is then sent on subsequent requests to the server and the server compares it with the stored session data and proceeds to process the requested action.

![](https://cdn-images-1.medium.com/max/800/0*P5OxJMihg0S0jyqk.png)


## What is token based authentication?
Token based authentication is one in which the user state is stored on the client. This has grown to be the preferred mode of authentication for RESTful APIs. In the token based authentication, the user data is encrypted into a JWT (JSON Web Token) with a secret and then sent back to the client.
The JWT is then stored on the client side mostly localStorage and sent as a header for every subsequent request. The server receives and validates the JWT before proceeding to send a response to the client.

    headers:{
    "Authorization": "Bearer ${JWT_TOKEN}"
    }
- A typical example of how the token is sent with the header to the server
![](https://cdn-images-1.medium.com/max/800/0*16xpkdbQ1tuFphvs.png)


## When to use?
There really isn’t a preferred method for authentication, both methods can be used interchangeably or together to create a hybrid system. It all boils down to the developer and the use case.
However, it is worth noting that token based authentication scales better than that of a session because tokens are stored on the client side while session makes use of the server memory so it might become an issue when there is a large number of users using the system at once.