File Extension File Extension Guide

What is an ICS File?

ICS files are iCalendar files, plain text files that carry calendar events. RFC 5545 defines the format and Outlook and Google Calendar both import it. One .ics file can hold a single meeting or a whole calendar.

iCalendar File 📝 Plain Text 📜 RFC 5545 📅 Events and Calendars

Open an ICS File →

See Inside an ICS File →

.ICS

iCalendar Event File

Format:iCalendar, RFC 5545
Content:Plain text
Starts with:BEGIN:VCALENDAR
Line ending:CRLF
Imports into:Outlook, Google Calendar
Editable in:Any text editor

📋 In This Guide

What is ICS? Inside an ICS File Create an ICS File Open an ICS File Import Into Outlook Import Into Google Where ICS Comes From Compared FAQs

📖 What is an ICS File?

ICS files are iCalendar files. Each one is a plain text file that lists calendar events in a fixed layout defined by RFC 5545. Outlook and Google Calendar both import the format. A single .ics file can hold one meeting or a whole calendar.

RFC 5545 appeared in September 2009 and replaced the older RFC 2445. Meeting invitations, calendar exports and calendar downloads on websites all use the .ics extension, which is why the file turns up in so many places.

One rule to remember

Read an unknown .ics file in a text editor before you import it. The file is plain text, so the editor shows every event, organizer and link that the import would add.

🔬 What is Inside an ICS File?

Every .ics file wraps its content in BEGIN:VCALENDAR and END:VCALENDAR. Each event sits between BEGIN:VEVENT and END:VEVENT. One complete event looks like this sample.

# One event in an .ics file

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Example Corp//Calendar//EN
BEGIN:VEVENT
UID:20261022T100000Z-001@example.com
DTSTAMP:20261022T093000Z
DTSTART:20261105T090000Z
DTEND:20261105T100000Z
SUMMARY:Project review
END:VEVENT
END:VCALENDAR
  • VERSION and PRODID. VERSION:2.0 names the iCalendar version and PRODID names the program that wrote the file.
  • VEVENT. One event with a UID, a DTSTAMP time and a start in DTSTART. DTEND and SUMMARY add the end and the title.
  • Other components. RFC 5545 also defines VTODO for tasks, VJOURNAL for notes, VFREEBUSY for availability and VTIMEZONE for time zones.
  • Line rules. Lines end with CRLF and should not pass 75 octets. Longer lines wrap with a CRLF followed by one space or tab. Parsers remove that break when they read the file.

✍️ How do You Create an ICS File?

An .ics file is plain text, so any text editor can create one. Each event needs its own UID, a DTSTAMP and a DTSTART between BEGIN:VEVENT and END:VEVENT. RFC 5545 separates lines with CRLF, which is the line ending Windows Notepad writes.

  1. Open Notepad and type the BEGIN:VCALENDAR, VERSION:2.0 and PRODID lines.
  2. Add one VEVENT block for each event and give each block a different UID.
  3. Finish with the END:VCALENDAR line.
  4. Choose Save As, set the file type to All files and name the file team.ics.
  5. Import the file into a spare calendar first to check the dates.

🔓 How do You Open an ICS File?

Three routes cover most needs. Read the file as text first when you do not know the sender, then import it into the calendar you use.

Read it as text

Open the file in Notepad or any text editor. The lines follow the BEGIN:VCALENDAR layout of RFC 5545, so you can read titles, times and locations without touching a calendar.

Preview before importing

The Univik ICS file viewer shows the events in a .ics file before anything reaches your calendar.

Import into a calendar

Outlook and Google Calendar import .ics files through a built-in import wizard.

📧 How do You Import an ICS File Into Outlook?

Microsoft lists these steps for importing calendars into Outlook and applies them to Outlook for Microsoft 365, Outlook 2024 and Outlook 2021.

  1. Click File, then Open & Export, then Import/Export.
  2. In the Import and Export Wizard choose the iCalendar (.ics) type and click Next.
  3. Select the .ics file on your PC and click OK.
  4. Click Open as New. Outlook imports the file as a new calendar.

🗓️ How do You Import an ICS File Into Google Calendar?

Google lists the steps for importing events into Google Calendar. The import works on a computer.

  1. Open Google Calendar in a web browser and click Settings, then Settings again.
  2. Click Import & Export in the left menu.
  3. Click Select file from your computer and choose the .ics file.
  4. Pick the destination calendar and click Import.

What Google does not import

Guests and conference data stay behind. Imported events do not stay in sync between accounts. A .zip file needs extracting first so each .ics file imports on its own. The file must begin with BEGIN:VCALENDAR and end with END:VCALENDAR.

📥 Where do ICS Files Come From?

  • Calendar exports. Calendar apps export events as .ics files for backups and for moves between accounts.
  • Meeting invitations. Email invitations often carry an .ics attachment that adds the meeting to a calendar.
  • Foxmail calendars. Univik Foxmail Converter exports Foxmail calendar entries as ICS files, as Export Foxmail Calendar explains. The companion format for contacts is VCF, described in the VCF file guide.
  • Converted files. The ICS converter turns .ics events into CSV, Excel and other formats for reports and moves.

⚔️ How does ICS Compare With Other Calendar Formats?

FormatWhat it isOpens in
.icsiCalendar text file, defined in RFC 5545Outlook and Google Calendar import
.vcsOlder vCalendar fileOutlook import wizard lists it as a separate type
.csvSpreadsheet rows with English headers such as Subject and Start DateGoogle Calendar import
.pstOutlook data file with a calendar folder insideOutlook, see the PST file guide

📝 Summary

  • .ics is a plain text iCalendar file
  • RFC 5545 defines the layout
  • Files start with BEGIN:VCALENDAR
  • Each event sits in VEVENT lines
  • Outlook imports through File, Open & Export
  • Google Calendar imports under Import & Export
  • Google skips guests and conference data
  • A text editor shows what an import would add

Last updated 22 October 2026. Format rules come from RFC 5545. Import steps come from Microsoft and Google.

❓ Frequently Asked Questions

An ICS file is an iCalendar file, a plain text file that holds calendar events in the layout that RFC 5545 defines. Outlook and Google Calendar import it. One file can hold a single event or a whole calendar.

Import it into a calendar app or open it in a text editor to read it. Outlook uses File, Open & Export and Import/Export while Google Calendar uses Settings and Import & Export. A text editor shows every event line without changing your calendar.

In Outlook for Microsoft 365, 2024 or 2021 go to File, Open & Export and Import/Export, choose the iCalendar (.ics) type and select the file. Choosing Open as New imports the file as a new calendar.

Open Google Calendar on a computer and choose Settings, then Import & Export. Select the file from your computer, pick the destination calendar and click Import. Guests and conference data are not imported.

BEGIN:VCALENDAR opens the iCalendar object and END:VCALENDAR closes it. Google Calendar requires an iCalendar file to begin and end with these two lines. Events sit between BEGIN:VEVENT and END:VEVENT inside.

Open it in a text editor, because an .ics file is plain text. Read the SUMMARY, DTSTART and LOCATION lines of each event and look at any URL or organizer lines when the sender is unknown.

No, Google Calendar says imported events do not stay in sync between accounts. A change in the source calendar does not update the imported copy.

Type the BEGIN:VCALENDAR header, one VEVENT block for each event and the END:VCALENDAR line in a text editor. Give every event its own UID and save the file with the .ics extension.

ICS holds iCalendar data and VCS holds the older vCalendar format. The Outlook import wizard lists the two as separate choices.

Google Calendar asks you to extract a .zip file first and import each .ics file separately.