On your devices. Your dashboards, widget parameters, reminders, the data your tools fetch and record, and your credentials are all stored on your devices.
Our servers handle: delivering tools for download; sign-in, including a list of your signed-in devices for you to manage; Pro purchases and free trials; and receiving the reports and feedback you choose to send.
If you allow a tool to send server notifications, our servers also keep the device push token needed to deliver them and which tools you've allowed, so they can pass that tool's notifications on to you. They don't keep the notification content.
With Sync across devices on, they also keep a copy that was encrypted on your device, so it can reach your other devices; we can't decrypt it. Credential names and the websites they're used for sync too, but not their values. Values sync, encrypted, only if you turn on Sync keys and credentials. Services you connected by signing in need to be connected once on each device.
When you switch devices, export a backup from Me › Backup & Restore on the old device and restore it on the new one. If you use Sync across devices, just sign in to the same account on the new device and join sync. For security, credentials aren't included in backups, so you'll need to connect them again.