If you use the iOS SDK or the Android SDK, user interactions and events tracked while the user is offline are queued, and will be tracked in Matomo as soon as the user comes back online.

If you use the JavaScript Tracker in your web application, currently user interactions and events while the user is not connected to the Internet are not tracked and discarded, however we’re currently working on offline support and this will be available in a few months, you can follow progress in this issue.