localStorage is a web storage feature that allows websites to store data in a user's browser. This data persists even after the browser is closed, making it useful for saving user preferences, session information, or any other data that should be retained across visits. It can hold key-value pairs, with each key being a string and the value being a string as well. Data stored in localStorage is accessible only to the same origin, meaning that only the website that created the data can read or modify it. This feature is part of the Web Storage API, which also includes sessionStorage, a similar storage option that only lasts for the duration of a page session.