FILE FORMAT GUIDE
ICS File (.ICS): What It Is & How to Open It
An ICS file stores calendar information in the iCalendar format. It can describe events, tasks and availability for exchange between calendar applications. Import it into a compatible calendar to use the entries; opening it as text only shows the underlying data, not a calendar view.
Quick facts
- Extension
- .ics
- Format
- iCalendar
- Category
- calendar
- MIME type
- text/calendar
- Standard / developer
- IETF
- Open with
- Calendar, Outlook.com / Outlook on the web
What is ICS?
iCalendar is an exchange format, not an application or a calendar account. Its components contain properties such as event dates and descriptions. Importing a file and subscribing to a calendar are different workflows: a one-time import does not automatically track later changes to the source calendar.
How to open ICS
CalendarmacOS
Drag the .ics file into Calendar, or choose File → Import, select the file and choose the calendar that should receive the events.
Outlook.com / Outlook on the webWeb
Use the calendar import workflow to upload an .ics file. Subscribe only when you have a calendar URL and want updates.
Common uses and compatibility
- Exchange calendar events
- Transfer a calendar between applications
Things to check
- Importing does not create a live subscription.
- Review dates and time zones before relying on imported events.
Technical details
- Signature
- Not reviewed
- Encoding
- UTF-8 (default)
- Container
- Not reviewed
- Compression
- Not reviewed
Related formats
- Email Message
An email can carry calendar data, but the saved EML message and an ICS invitation are different formats.
Sources & review
Sources reviewed 2026-09-18.