While internet cookies, commonly referred to as just "cookies," are widely recognized today, some companies also use Local Storage and Session Storage as other methods used by programmers to store persistent information in a visitor's browser. However, what's the main difference between cookies and local storage, and why choose one over the other? This article will help you with these questions!

As mentioned earlier, Cookies, Local Storage, and Session Storage are methods used through programming languages to store information in a website visitor's browser.

In other words, they store information in your browser about your access and how you navigate the website. Many of these have been used maliciously, even capable of storing all the information entered in text fields in forms, for example.

Few people know that cookies were originally developed by hackers to capture people's data on the internet. Later, this technology gained a commercial purpose and is now widely used across the web.

Before you get alarmed or want to reject all internet cookies and storage, remember, they make your life much easier.

Thanks to them, your products stay in the shopping cart when you switch tabs or go back to the store to add more items.

They keep a pre-filled form in case there's a connection glitch, preventing you from starting over.

And they also welcome you by recognizing your previous access, without needing to log in to your account hundreds of times a day.

Now that we've discussed the similarities, let's delve into the differences using three main criteria: storage capacity, storage location, data persistence, and performance.

- Storage Capacity

This capacity usually varies between browsers. In general, cookies can store up to 4096 bytes or 4KB, while Local Storage can handle 5MB, and Session Storage ranges from 5MB to 10MB.

Moreover, there's a maximum limit on the number of cookies per domain, and it's not recommended to exceed 30 cookies.

Some browsers, such as Opera, will prompt the user to allow more data usage when this limit is reached.

- Storage Location

Cookie information is stored in both the browser and the originating server of the referenced service.

Local Storage and Session Storage use only the browser as the storage location for data.

- Data Persistence

Data persistence refers to HOW and WHEN the stored information is deleted, erased, or invalidated.

Cookies

Cookies have an expiration date, causing the stored information to become invalid and outdated when that date is reached. However, whenever a visitor deletes cookies from a website, that information is also removed from the browser.

Some browsers automatically clear cookies periodically, and you can usually configure this in settings.

Learn how to clear cookies and browser cache.

Today, due to privacy regulations like LGPD, GDPR, and CCPA, websites using these trackers must inform their visitors of their existence using a cookie banner. This technology, called a CMP (Consent Management Platform), must then block cookies based on user consent.

To learn all about GDPR, CCPA, and LGPD, we have this article for you.

Local Storage

Local Storage has no expiration date, so the information persists in the browser until the user performs a cleanup and deletion. Additionally, there are fewer browsers that offer features to block or periodically delete Local Storage data.

Regarding privacy regulations, especially GDPR, the same obligation to inform its usage applies to Local Storage. Therefore, when choosing your cookie banner, ensure that it also lists third-party tracker Local Storage used on your site.

To learn more about how a CMP works, here's an article to help you understand.

Session Storage

In Local Storage, information remains stored until a deletion is performed. However, in Session Storage, the information is automatically deleted whenever the visitor leaves the site or closes the browser tab.

This is the main difference between Local and Session Storage.

- Performance

To analyze performance between web storage (Local and Session) and cookies, a highly technical language would be necessary. However, let's try to simplify the facts.

Every website has a visually coded part connected to a server. The server keeps the site online, and when someone accesses that URL, it operates those visual settings and responds to interactions on the screen.

This interaction is performed by the browser (Chrome, Safari, Opera, Brave...)

If your browser has cookies from that site, in addition to communicating with the site's server, it must also await the server's reading of those cookies and their respective servers. This is because there may be cookies from that specific site and cookies from third-party companies installed.

Therefore, when using cookies, all requests you make to the site also depend on sending cookie information to your origin server and then to the site. Hence, simply using a cookie in your application consumes a bit more "bandwidth" and "data" to read and execute it on the site, and present it in the browser.

In contrast, Local and Session Storage do not require this triangulation between servers, resulting in less bandwidth needed for the site to respond to the information contained in web storage.

Want to learn more about how a LGPD cookie banner works? In this link, I explain the step-by-step of the technology developed by AdOpt and used on thousands of websites.

After all, if your site uses cookies, you can't simply ignore LGPD. You need to choose a strategy to avoid the fines associated with this new legislation.