'Offline First' is a design philosophy for web and mobile applications that emphasizes the need for applications to work seamlessly, even when an internet connection is not available. The approach focuses on ensuring the core functionality of an application remains intact offline.

This approach can improve the user experience significantly, particularly in scenarios where an internet connection is unstable, slow, or entirely absent. Applications designed with an Offline First strategy use service workers and local data caching to ensure that users have access to critical functionality and data at all times.