.ics

What is a .ics file?

ICS is a universal calendar format — shareable events and schedules supported by Google Calendar, Apple Calendar, and Outlook.

Safe format
Type Misc
By IETF
MIME text/calendar

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What is it

Someone sent you an event invitation and it arrived as an .ics file. Double-click it and your calendar app (Google Calendar, Apple Calendar, Outlook) offers to add the event. That's ICS working exactly as designed — a universal calendar format that every calendar application speaks.

iCalendar (the format's official name, not to be confused with Apple's calendar app) was standardised as RFC 5545. An ICS file contains events with start times, end times, locations, descriptions, attendees, recurrence rules, and reminders — all in a structured text format. You can open an ICS file in a text editor and read the event details directly. Calendar subscription URLs (the ones that keep your calendar in sync with external schedules) serve ICS data over HTTP.

Every major calendar application imports ICS — Google Calendar, Apple Calendar, Microsoft Outlook, Thunderbird. To add an event, double-click the file or drag it into your calendar. For creating ICS files, most calendar apps can export events as ICS. Developers use libraries like ical.js to generate ICS programmatically for event invitations and booking systems.

Technical details
Full Name
iCalendar File
MIME Type
text/calendar
Developer
IETF
Magic Bytes
N/A
Safety
.ics is a known, safe format.
What opens it
Google Calendar
FREE Web
Apple Calendar
FREE macOS / iOS
Microsoft Outlook
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FAQ
How do I add an ICS event to Google Calendar?
Open Google Calendar in a browser, click the gear icon → Settings → Import & Export → Import. Select the .ics file and choose which calendar to add it to. On mobile, opening an .ics file typically offers a direct 'Add to Calendar' option.
Can I subscribe to a recurring ICS calendar?
Yes. Many services provide ICS subscription URLs (sports schedules, academic calendars, booking systems). In Google Calendar: Other Calendars → From URL. The calendar stays in sync automatically.
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