What is the VCS file format?
.vcs is a file extension associated with the vCalendar format, which is related to the .vcf vCard standard. .vcs files store calendar entries and can be used to share scheduling data between users. Each file records information such as the name of the event, event start/end times, location, and a short description.
Every .vcs file is plain text that begins with the line BEGIN:VCALENDAR and ends with END:VCALENDAR. The property VERSION:1.0 inside the file identifies it as vCalendar, distinguishing it from the newer .ics iCalendar format, which carries VERSION:2.0.
The main usage of .vcs is importing and exporting events, schedules, or appointment data. The format is supported across mobile devices, office suites, and various organizer tools - though it is now considered a legacy standard. .vcs files are still supplied by some event organizers as a means of sharing event information with other users or group members.
vCalendar 1.0 was published in 1996 by the Versit Consortium (Apple, IBM, Lucent, and Siemens) and has since been superseded by iCalendar 2.0 (.ics, IETF RFC 5545). Most modern calendar applications still import .vcs for backward compatibility but save new appointments as .ics. Non-ASCII text in older .vcs files is typically quoted-printable-encoded and may appear garbled when opened in a plain text editor.
Security & safety
RISK: LOWA .vcs is plain text and cannot execute code, so the file itself is low risk. The real risk is social, like any calendar invite: an unsolicited .vcs can auto-add a spam event with phishing links or fake reminders to your calendar. Treat unexpected invitations like unexpected email - don't click links inside an event you weren't expecting. A purely cosmetic issue: old vCalendar files use quoted-printable encoding, so accented text can look garbled in a plain editor but displays correctly once imported.
Format details
in a nutshell- Visual Studio C++ Project (.vcxproj predecessor) / makefiles - Some build/config tooling has used .vcs, but the dominant meaning here is the vCalendar appointment file.
- ScanSoft / OmniPage settings - Rare legacy application settings have used .vcs; unrelated to the calendar format described here.
Programs that open VCS files
Windows3 apps
Microsoft Outlook
Paid Double-click the .vcs to open it as an appointment, then Save & Close to add it to your calendar. 
Mozilla Thunderbird
Open-source Open the .vcs with Thunderbird's built-in calendar to import the event. 
Windows Calendar (new Outlook / Mail and Calendar)
Built-in Double-click the file; the built-in Calendar app offers to add the event. 
macOS2 apps
Apple Calendar
Built-in Double-click the .vcs; Calendar asks which calendar to add the event to. (Formerly named iCal, renamed Calendar in 2012.) 
Linux1 app
GNOME Calendar / Evolution
Open-source Open the .vcs in Evolution or GNOME Calendar to import the event. 
Android1 app
Google Calendar / default calendar
Free Tap the .vcs attachment; Android offers to add the event to a calendar. 
Google Calendar
Free Settings (gear) > Import & export > Import; choose the .vcs and a target calendar. (Google may prefer .ics - convert if rejected.) Technical details
deep spec| MIME type | text/x-vcalendar |
| Text encoding | ASCII or UTF-8; legacy files frequently use quoted-printable encoding for non-ASCII characters |
| File structure | Line-based PROPERTY:VALUE pairs wrapped in BEGIN:VCALENDAR and END:VCALENDAR delimiters |
| Internal version marker | VERSION:1.0 - identifies the file as vCalendar (VERSION:2.0 indicates the newer .ics iCalendar format) |
| Date/time format | ISO 8601 compact notation - YYYYMMDD for dates, YYYYMMDDTHHmmssZ for UTC timestamps |
| Supported block types | VEVENT (calendar event) and VTODO (task or to-do item) |
| Core event properties | SUMMARY (event name), DTSTART, DTEND, DESCRIPTION, LOCATION, AALARM (audio alarm trigger) |
| File delimiters | Every file opens with BEGIN:VCALENDAR and closes with END:VCALENDAR; no binary magic bytes exist |
| Typical file size | Under 1 KB to a few KB - normally holds a single event or appointment |
| Developer/origin | Versit Consortium (Apple, IBM, Lucent, Siemens), 1996; later maintained by the Internet Mail Consortium |
| Superseded by | iCalendar 2.0 (.ics), standardized as IETF RFC 2445 (1998) and revised by RFC 5545 (2009) |
| Platform support | Windows, macOS, Linux, Android, iOS; Palm OS and early Symbian devices (historical) |
| Modern app behavior | Most current calendar applications import .vcs for backward compatibility but export new appointments as .ics |
| Released | 1996 (vCalendar 1.0 specification) |
| Latest version | vCalendar 1.0 (final; superseded by iCalendar 2.0 / RFC 5545) |
| Open standard | Yes · royalty-free |
| Specification | www.imc.org |
VCS conversions
Community Q&A
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