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Using local storage

What is local storage?

In web development, local storage is a type of storage that allows web applications to store data locally within the user’s browser. It is a persistent data storage mechanism that allows data to be saved across browser sessions, allowing web applications to maintain state even after the browser has been closed and reopened.

How to use local storage

Local storage is implemented using the localStorage object in JavaScript, which is part of the Web Storage API. It allows web applications to store key-value pairs of data in the form of strings, with the keys being strings and the values being any serializable JavaScript object.

To use local storage, you can set values using the setItem() method and retrieve them using the getItem() method. For example:

localStorage.setItem('key', 'value');
const value = localStorage.getItem('key');

You can also remove items from local storage using the removeItem() method, or clear all items from local storage using the clear() method.

Local storage is useful for storing data that needs to be persisted across browser sessions, such as user preferences or application state. It is important to note, however, that local storage is limited in size and may not be suitable for storing large amounts of data.

Keep in mind that local storage is shared between all Red Apps, hence keys should be unique as possible, e.g. prefixed with Red App name. For the same reason you should not use clear() method from the Web API, instead remove keys one by one.

Local storage vs session storage

Local storage and session storage are both types of web storage that allow a website to store and retrieve data in the user’s browser. However, they have some differences:

  1. Persistence: Local storage is persistent, meaning the data stored in local storage remains in the browser even after the browser is closed. In contrast, data stored in session storage is only available for the current window or tab, and is deleted when the window or tab is closed.

  2. Scope: Local storage is available to all windows and tabs from the same origin (website), while session storage is only available to the current window or tab.

  3. Size: Local storage has a larger maximum size than session storage, typically around 5MB. Session storage has a smaller maximum size, typically around 2MB.

  4. Access: Both local storage and session storage can be accessed using the localStorage and sessionStorage objects in JavaScript, respectively.

In general, you can use local storage for data that you want to persist beyond the current session, such as user preferences, while session storage is more suitable for temporary data that only needs to be available during a single browsing session.


It is important to be aware that local storage is not a secure storage solution.

Local storage stores data as plain text, so any data stored in local storage can be accessed by any JavaScript code that is executed within the same origin as the web application that stored the data. This means that if an third party is able to execute JavaScript code on your web application, they may be able to access data stored in local storage.

Additionally, local storage data is persisted even if the user closes the browser or clears their browsing history, so data can be compromised even after the user has left the web application.

For these reasons, it is generally not recommended to store sensitive or confidential information in local storage. If you need to store sensitive data (e.g. PCI/GDPR data) in a web application, you should consider using a more secure storage solution.

Additional information