What is an .ics file? A simple guide
Understand the calendar file used across email and scheduling apps.
Published 1/5/2025
What is .ics?
.ics is the most widely used file extension for iCalendar data (RFC 5545). The file is plain text, structured into components like events, alarms, and time zone definitions. This simple, open format lets different apps exchange calendars without a proprietary lock‑in.
A single file may contain one event (e.g., a meeting invite) or an entire schedule (e.g., a sports league season). Because it’s text, it’s easy to email, host, or generate on the fly.
Import vs. subscribe
Importing copies events into your calendar once. Subscribing follows a URL and keeps events updated over time. If you expect changes, prefer subscription; if the schedule is final (like a past conference), a one‑time import is fine.
Compatibility and quirks
Most calendar apps read .ics, but they differ in how they handle recurring rules, time zones, and reminders. That’s why the same file can look slightly different across apps, or fail to import if a field is malformed.
Privacy considerations
An .ics file can include event details like locations or attendees. If you didn’t expect to receive a file, treat it with caution and preview before importing.
Quick instructions (optional)
- iPhone/iPad: In ICSKit, open Add ICS to Calendar, select the file from Files/iCloud, then choose your calendar.
- Google Calendar (web): Settings → Import & export → Select
.ics→ Choose calendar → Import. - Outlook: Desktop: File → Open & Export → Import/Export. Web: Add calendar → Upload from file.
- Apple Calendar (Mac): File → Import → choose the
.ics.