What is an ICS file?

An ICS file is a plain text file that holds calendar events. The format is an open standard called iCalendar, and every major calendar app reads it, including Google Calendar, Apple Calendar and Outlook. The file name normally ends in .ics.

What is inside one

Each event in the file carries a title, a start and end time, and usually a location and a description. It can also carry a time zone and a unique id, which is what lets a calendar app recognise an event it has seen before and update it in place rather than creating a duplicate.

Subscribing is not the same as importing

This is the single most useful thing to understand about ICS files, and it catches a lot of people out.

• Importing copies the events into your calendar once. It is a snapshot. If the original changes later, your copy does not.
• Subscribing points your calendar app at a web address that serves an ICS file. Your app re-reads that address on a schedule, so when the source changes your calendar follows.

For anything with a schedule that moves, such as sport fixtures or a TV season, you almost always want to subscribe rather than import. A broadcaster moving a kick-off time is normal, and an imported copy will quietly be wrong.

How to open an ICS file

Double-clicking an .ics file opens it in your default calendar app and offers to import the events. That is fine for a one-off, such as a single meeting invitation someone emailed you.

If instead you have a link to an ICS file, do not download it. Add it as a subscription. See how to add a calendar to Google Calendar or how to add a calendar to Apple Calendar.

Where Sync2Cal fits

Sync2Cal maintains ICS feeds for several thousand calendars and keeps them current, so you subscribe once and stop thinking about it. That covers sport such as the FIFA World Cup 2026 and every NFL team, plus TV shows, finance and public holidays. You can browse everything here.

If you are new to it, how to subscribe to your first calendar walks through it end to end.