Is my data secure (encrypted)?

NotePlan doesn't encrypt your notes but saves them locally on your device. CloudKit or iCloud Drive are used to synchronize your notes across your devices. Both are services maintained by Apple. So, during the sync process (upload & download), and while being stored in the cloud, Apple handles encryption, if any.

As the developer, we have no access to your data. Your data can be accessed only with your private Apple ID. Apple employees should also have no access to your data.

Additionally, to secure the locally saved data, you can enable "FileVault" in you system preferences: