Privacy
Short, because there is not much to say.
What stays on your device
Your settings and your recent words are stored in your browser's local storage, under the
keys pl_prefs_v1 and pl_history_v1. They never leave the device.
Clear everything in Settings removes both.
Playing a device voice involves no network request at all — your browser speaks it locally.
What is sent to the server
Playing a server voice sends one request containing the word you typed, the voice you chose and the speed. That is the whole payload. The audio comes back and the request is over.
Requests are counted per IP address for a minute at a time, purely to stop one client flooding the synthesiser. That count lives in memory and is not written anywhere.
What is not collected
Server logs
Whoever operates this instance controls its logs. A standard web server records IP addresses and requested URLs, and a synthesis request has the word in its URL. If you run this yourself, that is yours to configure.