Online travel operators are trying to beat Airbnb at its own game, and it is starting to work.
Booking.com, the online travel site under Booking Holdings, says it now has 5 million properties in its non-hotel portfolio, a 27 percent jump from last year. The 5 million includes villas, houses and apartments. Booking Holdings CEO Glenn Fogel told CNBC that the alternative accommodations category is currently its fastest growing market.
Booking.com's 5 million puts it ahead of Airbnb's 4.85 million listings. Airbnb says it anticipates surpassing 5 million listings by the end of June.
A spokesperson for Airbnb told CNBC via email, "Airbnb is growing faster and spending less because we have a community model as opposed to Booking's commodity model."
Either way, the race is intensifying between privately held Airbnb and publicly listed Booking Holdings and Expedia. Expedia acquired HomeAway in 2015 for nearly $4 billion to better compete in the alternative lodging space and rival Airbnb.
But perhaps all three players will carve out a piece of the pie.
As consumers increasingly look to book a house or an apartment for their vacation, analysts say the non-hotel business will continue to boom, creating opportunity for multiple travel operators that target specific preferences.
"We project Alternative [accommodations] to double in three years to $86 billion," wrote Kevin Kopelman, director and research analyst at Cowen & Co., in a note sent to clients in late February.
Kopelman sees Airbnb's strength in urban homes, Booking's in multi-unit and other professionally managed properties, and Expedia's HomeAway in North America vacation homes.
One risk in continuous expansion into this new market will be added costs, which Kopelman says could weigh on margins for the online travel sector.