Valve announced that year-over-year new user growth has increased by 178%, with a sales increase of 200% over the last 12 months.
The service has three million users playing games simultaneously and over six million unique users accessing Steam each day.
To cater for the growth, the infrastructure has been increased to run at 400Gps, which is enough to send a digital version of the Oxford English Dictionary 92.6 times per second.
"Steam is on track to record the biggest year in its six-year history," said president Gabe Newell.
"The year has marked major development advances to the platform with the introduction of support for Mac titles, the Steam Wallet and in-game item buying support, and more.
"We believe the growth in accounts, sales and player numbers is completely tied to this work and we plan to continue to develop the platform to offer more marketing, sales and design tools for developers and publishers of games and digital entertainment."
Steam first launched in 2003 and was a compulsory install with Half-Life 2 a year later.