ICS files are used by programs and systems which implement user calendar feature, for example, applications such as Microsoft Outlook, Apple iCal, Google Calendar.

ICS format is designed as a standard format for sharing calendar data between different applications that support it. ICS files can be imported and exported from applications that support calendar feature. Importing of ICS files should not be confused with ICS or iCal subscriptions, which are features that allow automatic updating of calendar data. Many different ICS calendars that list interesting events can be downloaded from the internet and imported to the personal calendar.