Understanding LocalStorage vs SessionStorage vs Cookies

When it comes to client-side storage in web applications, three primary methods come into play: LocalStorage, SessionStorage, and Cookies. While each serves the purpose of storing data, they differ significantly in how and when they should be used.

 

LocalStorage is designed to store data persistently, which means that even after the browser is closed, the stored data remains accessible. Consequently, it is ideal for storing data that does not need to expire, such as user preferences. Data is stored as key-value pairs in the browser, and a simple example would be:

// Storing data
localStorage.setItem('username', 'JohnDoe');

// Retrieving data
const username = localStorage.getItem('username');

 

SessionStorage, on the other hand, works similarly to LocalStorage, but with a key distinction. Indeed, data stored in SessionStorage only lasts for the duration of the browser session. Therefore, once the browser or tab is closed, the data is automatically deleted. It is perfect for temporary data, like form inputs that should not persist across sessions. An example would be:

// Storing data
sessionStorage.setItem('sessionID', '12345');

// Retrieving data
const sessionID = sessionStorage.getItem('sessionID');

 

Cookies are generally used for storing small amounts of data that need to be sent back to the server with each request. Although they can expire after a set period, cookies are usually chosen when data needs to be shared between the client and server, such as authentication tokens. An example of setting a cookie would be:

// Setting a cookie
document.cookie = "authToken=abcdef; expires=Fri, 31 Dec 9999 23:59:59 GMT;";

// Retrieving a cookie
const cookies = document.cookie;

 

Conclusion:

LocalStorage is best for persistent data, SessionStorage is suitable for temporary data within a session, and Cookies are preferred for small, server-related data. Thus, choosing the right storage method depends on the nature and lifespan of the data being stored.