What technology allows web applications to store data on the client side to improve performance?

The Web Storage API is designed specifically for web applications to store data on the client side, thereby enhancing performance and user experience. It provides two primary storage types: local storage and session storage. Local storage allows data to persist even when the user closes the browser, making it ideal for saving user preferences and other relevant data without requiring requests to the server.

By leveraging the Web Storage API, developers can reduce the need for frequent server communication, which can lead to faster loading times and a more responsive application. This type of client-side storage allows applications to cache data effectively, reducing latency and improving performance for users by minimizing the time spent waiting for network requests to complete.

While cookies are also capable of storing data on the client side, they have limitations regarding size and are sent with every HTTP request, which can slow down the performance. Data caching typically refers to storing data temporarily to avoid repeated fetches from the server, but it is not an API or method for persistent storage on the client side in the manner that the Web Storage API provides. A local server is unrelated, as it pertains to where applications are hosted rather than how data is stored on the client.