Yes. All your data stays on your device. Tracker data is stored in your browser's local storage. Nothing is sent to a server. No account exists. Nobody can see your collection.
Step 1
There's no account, no email, no password, no personal info involved. You use the site anonymously. There's nothing to identify you through the tracker.
Step 2
Local storage is a standard browser feature. It saves data directly on your device. Your catches, shinies, and notes are never uploaded, synced, or shared with anything external.
Step 3
Because there's no server-side storage, there's no database of user collections that could get breached. Your data can't be accessed by anyone.
Step 4
Export downloads a JSON file directly to your device. Import reads a local file. Both happen entirely on your machine. No server in the middle.
Step 5
The trade-off: you're responsible for backups. Browser data cleared means progress gone, unless you have an export saved somewhere.