Glossary

ICS file

The standard calendar file format (iCalendar) that every major calendar app can read.

An ICS file is a plain-text file containing calendar events in the iCalendar format, standardized as RFC 5545. Each event carries a title, start and end time, location, and identifiers that let apps recognize updates to the same event.

ICS files come in two flavors in practice: a one-time file you import (a snapshot), and a hosted ICS feed you subscribe to (a live connection that keeps updating). The file extension and format are identical; the difference is whether your app checks the URL again later.