iCloud: Calendar app on Mac (or iCloud.com) → right-click the shared calendar → Sharing Settings… → tick Public Calendar → copy the webcal://… link.

Outlook / Office 365: Calendar → Settings → Shared calendars → publish the calendar → copy the ICS link.

Paste the link above and press Load calendar.

How the fetching works & privacy: browsers can't read these feeds directly (CORS). For a reliable, private setup, deploy the included Cloudflare Worker, which fetches the feed on its own server and keeps the secret token off this page — then put the Worker URL in DEFAULT_ICS_URL at the top of this file, or paste it above. Without a Worker, the page falls back to public relay proxies, which are less reliable and route the data through a third party — for anything sensitive, prefer the Worker or the Upload .ics button instead.