We forecast that online travel spending will reach $1 trillion by 2023, powered by growing online spending in air and hotel categories that account for 66% of total travel spending. This forecast details online travel growth across four categories (air, hotel, car rental, and rail) and 17 markets: Argentina, Australia, Brazil, Canada, China, France, Germany, India, Japan, Mexico, Netherlands, Russia, South Korea, Spain, Sweden, the UK, and the US.