Open ICS File

Information, tips and instructions

Open ICS File

ICS file extension is used by iCalendar internet standard to store events, to-dos, free/busy information and journal entries. The ICS file format is defined in RFC-5545 specification.

iCalendar is a protocol independent standard. It means that events could be shared using different transports including e-mail, HTTP protocol and others.

To open ICS file you can either use a calendar application of your choice or if you don’t have one you can open ICS file in a text editor and view information inside. Since information in iCalendar file format is stored as plain text it is possible to interpret information inside ICS file without special software. But it is still recommended to use one of the available calendar applications since they can read information in ICS file and display it in an easy to understand way. Editing calendar data in a specialized software is also much easier.

iCalendar standard is used by many online internet calendaring and scheduling applications including:

To display iCalendar events in HTML pages hCalendar microformat was developed. Using hCalendar microformat on a web page allows any software which parses the page to correctly read and interpret calendar events information. There are two different microformats for displaying iCalendar information. One is hCalendar which is based on “span” and “abbr” HTML tags. The other one is microformats2 update which uses “time” HTML tag. Microformats2 version is considered more suitable because of accessibility problems with original hCalendar version.

Besides ICS file extension iCalendar also uses IFB file extension to store information about free/busy time.

iCalendar is based on vCalendar created by the Internet Mail Consortium (IMC). vCalendar used VCS file extension for calendar data transfer.

Below is an example of calendar data file stored in iCalendar file format:
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//hacksw/handcal//NONSGML v1.0//EN
BEGIN:VEVENT
UID:[email protected]
DTSTAMP:19970714T170000Z
ORGANIZER;CN=Test User:MAILTO:[email protected]
DTSTART:19790714T170000Z
DTEND:19790715T035959Z
SUMMARY:Test Event
GEO:48.85299;2.36885
END:VEVENT
END:VCALENDAR

ICS files are transferred over e-mail or internet using text/calendar multipurpose internet mail extensions (MIME) type.