Saved only in this browser (localStorage) — never sent anywhere except directly to each platform when you post. X/Twitter isn't included: posting there needs a paid API tier and server-side request signing, unlike these three.
Server Settings → Integrations → Webhooks → New Webhook → Copy URL.
Settings → App Passwords → Add app password. Not your main login password.
Preferences → Development → New Application → check "write:statuses" → save, then copy "Your access token".
Nothing posted yet.