There are variety of options available for storing data within an Ionic app.
Here are two official Ionic options:
Ionic Secure Storage
For teams building mission-critical apps or requiring encryption support, Ionic Secure Storage is an official premium solution from the Ionic team that provides a cross-platform data storage system that works on iOS and Android.
It makes it easy to build high performance, offline-ready Ionic apps across iOS, Android, and the web.
For developers not requiring encryption nor relational data support, @ionic/storage is an open source key/value API for building apps that work across storage engines on multiple platforms.
Additionally, Ionic Secure Storage has a driver that works with the key/value API in
@ionic/storage while providing encryption and SQLite support.
Learn more about @ionic/storage