Facebook has finally filled its empty chief technical officer position. The company today promoted Mike Schroepfer from vice president of engineering to CTO, according to AllThingsD.

Schroepfer joined Facebook in 2008, after leading the development of the Firefox browser at Mozilla.
As vice president of engineering, Schroepfer was in charge of engineering and infrastructure, which means he made sure Facebook worked.
With this move, he's taking the empty seat left by former Facebook CTO Bret Taylor, who quit last June.