Holidu, the Munich-headquartered holiday rentals search engine that is now active in 21 country markets, has raised €40 million in Series C funding.

The round was led by Prime Ventures, with participation from coparion and MairDuMont Ventures. Existing investors, including EQT Ventures, Venture Stars, Senovo and business angel Chris Hitchen, also followed on.

Founded in 2014 by siblings Johannes and Michael Siebers after they say they had a frustrating experience trying to book a vacation rental for a surfing trip in Portugal, Holidu’s search engine lets you easily search for and book holiday accommodations.

Claiming to use proprietary image recognition technology, Holidu compares the prices of more than 15 million rental properties across 600 different websites, including Airbnb, Booking.com and HomeAway . This enables users to save “up to 55%” on their booking by automatically spotting price differences for the same property across various listings.

“Many of the sites offer the same rentals but at different prices,” Holidu co-founder and CEO Johannes Siebers told TechCrunch back in 2016. “Also, there is a large rate of rejected bookings as the different sites don’t synchronize calendars with each other and properties get double-booked. For consumers it is impossible to gain a transparent overview.”

To help solve this, Holidu has also developed a service for holiday property owners. Dubbed “Bookiply,” it offers a single interface to list properties on the largest travel websites, including synchronizing calendars, creating multilingual descriptions and sourcing professional photography. In addition, Bookiply’s team handles traveler communication.

Holidu says that Bookiply already manages 5,000 properties and claims it is the market leader in several European leisure destinations. “The focus is on property owners who are not yet online or whose digital presence can be optimised,” says the company.

Meanwhile, to boost growth, last year Holidu acquired its Spanish competitor Hundredrooms. The startup now claims 10 million visitors per month and says it will use the Series C funding for product development (both the Holidu website and the Bookiply software). It also will grow its Holidu partners and sign up more property owners to Bookiply. To achieve this, the company says it plans to open multiple regional offices.