Understanding Client-Side Storage for Web Apps: A Guide to Session, Local Storage, and Cookies

Photo by Denny Müller on Unsplash

Among the most important considerations building web apps make is how you should store your data. Whether you’re installing something on a user’s device or in the cloud, a good storage mechanism can be the difference maker. A good storage system saves your data reliably, minimizes the overall data payload sent over the network, and helps your app feel faster and more responsive. And if you’re making mobile web apps, the right caching strategy is critically important to be able to have offline experiences.

In this article, we will briefly glance over all types of available data storage for web applications, so that you know what will be appropriate for your application.

Session Storage -

Session storage is intended to hold data for one browser tab, every time you load a new page into a new tab the browser constructs a new “session” for that tab, so the information held in session storage will then be tied to that particular session.

One thing to remember about session storage is that it is preserved as long as the tab/browser is open. If one refreshes the page, or even navigates forward and backward within a session, the data remains, but when the tab is closed, the session is done, and all the data that’s saved in session storage gets cleared.

If you load the same URL in several tabs, each tab will have separate session storage. That is to say, if you duplicate a tab it will copy its session storage to the new tab.

Here’s an example of how you might use session storage in JavaScript in 5 easy lines:

// Save data to sessionStorage
sessionStorage.setItem('key', 'value');

// Get saved data from sessionStorage
let data = sessionStorage.getItem('key');

// Remove saved data from sessionStorage
sessionStorage.removeItem('key');

// Remove all saved data from sessionStorage
sessionStorage.clear();

Local Storage -

Local storage is very similar to session storage, but there’s one key difference: local storage persists even after the browser is closed. Data stored in local storage doesn’t expire, and it remains available until explicitly deleted.

One important thing is that local storage is supported in most current browsers, but its persistence might sometimes get messed up with the impact of such things as configuration of the browser, or the user deleting their cookies or history.

So, it’s kind of reliable mostly, but there are situations where local storage might unintentionally get wiped.

So, here is how you can use local storage:

// Save data to localStorage
localStorage.setItem('key', 'value');

// Get saved data from localStorage
const data = localStorage.getItem('key');

// Remove saved data from localStorage
localStorage.removeItem('key');

// Remove all saved data from localStorage
localStorage.clear();

Cookies -

Cookies are tiny pieces of data a server transmits to a client, and a client stores those pieces of data locally. The server will send back those pieces of data with subsequent requests. Primarily used for keeping track of the user’s state, such as retaining their login information when they log in and exiting to still be logged in, or remembering their last use settings.
There are three general applications for cookies:

1. Session Management : Cookies can be used for keeping users logged in, controlling the contents of shopping carts, and remembering game scores.
2. Personalization : Cookies can hold user preferences, themes, or settings that enhance their experience.
3. Tracking : Cookies are often used for tracking user behavior for analytics or to deliver targeted ads.

Cookies are a bit more restrictive than local and session storage, but they fill the requirement when you need to send data back to the server with each request.

Benefits of Client-Side Storage -

So, why do you need to care about client-side storage? Well, it has several benefits:

1. Personalization : You can store user preferences, such as theme settings, widgets, or font sizes, to customize the user experience.
2. Persistence : You can store things like the contents of a shopping cart, user logged-in status, or previous actions so that users do not lose track of their progress if they return to the site later.
3. Performance : The assets and data are downloaded locally meaning that your website could load relatively faster. This can be especially important with repeat visitors or sites the user access in an offline mode.
4. Offline Support : Client-side storage can be used to save documents or data so that users can access them even though they are not connected to the internet.

The bottom line is that client-side storage technologies such as session storage and local storage can store data to the user’s device and also make your web application more efficient and friendly. This serves faster apps which are easier and can work offline without making any request to the server.

I really hope that this breakdown of all the different storage options helps you understand when and how to use them in your web app.
Happy coding!