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July 15, 2026

vCalendar (vCal) vs ICS: What's the Difference?

Understand the history of calendar files, the difference between .vcs and .ics, and why modern systems use iCalendar.

vCalendar vs ICS: What's the Difference?

If you've ever dealt with calendar invites, you might have seen .vcs (vCalendar) files or .ics (iCalendar) files. While they serve the same fundamental purpose—sharing event data—they belong to entirely different eras of the internet.

What is vCalendar (.vcs)?

vCalendar was the original standard for electronic calendar data exchange, created in 1996 by the Internet Mail Consortium (IMC). It allowed people to send meeting requests via early email clients.

However, vCalendar was limited. It struggled with complex repeating events, timezones, and seamless cross-platform compatibility. Today, .vcs is considered obsolete, though some legacy enterprise systems (like very old versions of Outlook) may still occasionally generate them.

What is iCalendar (.ics)?

iCalendar (ICS) is the modern successor to vCalendar. Standardized in 1998 (and updated in RFC 5545), it solved the massive timezone and interoperability issues of vCalendar.

Almost every modern application in the world uses ICS files:

  • Google Calendar
  • Apple Calendar (macOS & iOS)
  • Microsoft Outlook & Exchange
  • Yahoo Calendar
// A standard ICS file header always denotes VERSION:2.0
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Invitly//EN
...

Which should you use?

You should always use ICS for sharing events today. It is the undisputed universal standard. Generating .vcs files will result in broken events on modern smartphones and web calendars.

Invitly strictly adheres to the RFC 5545 iCalendar specification, ensuring that your event links and downloads work perfectly whether your attendee is on an iPhone, an Android device, or a corporate Outlook desktop client.