What is iCal and How Does It Work for Vacation Rentals?
iCal is the format that lets Airbnb, VRBO, Booking.com, and Google Calendar share availability data. Understanding how it works explains why syncs sometimes lag - and what you can do about it.
What is iCal?
iCal (short for iCalendar) is a file format for sharing calendar data. It uses the .ics file extension and follows a standard defined in RFC 5545. It is supported by virtually every calendar application and booking platform in existence: Airbnb, VRBO, Booking.com, Google Calendar, Apple Calendar, Outlook, and hundreds of others.
For vacation rental hosts, iCal is the mechanism behind every calendar sync. When Airbnb "imports" your VRBO availability, it is fetching an iCal URL and reading the blocked dates from the file.
Why the name "iCal"?
The name came from Apple's iCal application (now called Calendar on macOS and iOS), which was one of the first mainstream apps to popularize the .ics format. The format itself is open and has nothing to do with Apple - it just stuck.What does an iCal file actually contain?
An iCal file is plain text. You can open one in any text editor. For a vacation rental platform, a typical file looks something like this:
BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Airbnb Inc//Airbnb//EN BEGIN:VEVENT DTSTART;VALUE=DATE:20260415 DTEND;VALUE=DATE:20260418 SUMMARY:Reserved END:VEVENT BEGIN:VEVENT DTSTART;VALUE=DATE:20260501 DTEND;VALUE=DATE:20260508 SUMMARY:Not available END:VEVENT END:VCALENDAR
Each VEVENT block represents a booked or blocked period. The SUMMARYfield might say "Reserved", "Airbnb", or "Not available" depending on the platform, but it never contains a guest name, phone number, or email.
iCal feeds do not expose guest data
A common concern from hosts is whether sharing an iCal URL reveals guest information. It does not. The feed only contains date ranges. Guest names and contact details are never included.How iCal sync actually works
When you give Airbnb a VRBO iCal URL to import, here is what happens:
- 1. Export: VRBO generates a permanent URL that always serves the current state of your VRBO calendar as a .ics file.
- 2. Import: You paste that URL into Airbnb's "import calendar" field. Airbnb stores the URL.
- 3. Polling: Airbnb periodically fetches the URL - typically every few hours - reads the blocked dates, and marks those nights as unavailable on your Airbnb listing.
- 4. Delay: Until Airbnb fetches the feed again, a new VRBO booking will not appear as blocked on Airbnb. This is the window where double bookings can occur.
The delay is built into how iCal works. There is no event-driven notification - each platform simply polls on its own schedule. Airbnb refreshes roughly every few hours; VRBO can take up to 24 hours.
What iCal sync cannot do
iCal is designed to sync one thing: which dates are unavailable. It is not a full integration. It cannot:
- Transfer pricing between platforms
- Sync listing descriptions, photos, or amenities
- Pass guest contact details between platforms
- Trigger instant availability updates (only polling)
- Cancel or modify existing reservations
For anything beyond date blocking, you need a channel manager with direct API connections to each platform.
Combining multiple iCal feeds
Each platform only imports one iCal URL at a time. If you list on three platforms, you can't give Airbnb three separate import URLs and have it merge them. The workaround is to use an iCal aggregator that merges multiple source feeds into a single URL - which is exactly what iCalendar Sync does.
Paste your Airbnb, VRBO, and Booking.com iCal URLs into the tool and you get back one combined URL. Import that single URL into all your platforms and each one sees all your bookings from all sources.