Booking.com

Booking.com is one of the largest online travel agencies. It is headquartered in Amsterdam, and is a subsidiary of Booking Holdings. Its mobile app is the most downloaded mobile app in the travel agency category, however it has some of the worst ratings on the internet with Trust Pilot rating it 1.4 stars. Booking.com provides lodging reservation services for approximately 3.4 million properties, including 475,000 hotels, motels, and resorts and 2.9 million homes, apartments in over 220 countries and territories and in over 40 languages. It also sells flights in 55 markets and tours and activities in more than 1,300 cities. However the success comes at a cost, many hotel partners say they don't get paid for months at a time, leaving small hoteliers out of pocket.