Feed-in tariffs (FITs), along with renewable electricity standards, are one of the most widely adopted renewable energy support policies around the world. As of 2013, 98 national and subnational governments had implemented FITs, nearly three times the number that had adopted them in 2004 (REN21 2015). In recent years, FIT activity has focused primarily on revisions to current policies, underscoring the need for stable and predictable, yet flexible, policy environments. This policy brief provides a primer on key FIT design elements, lessons from country experience, and support resources to enable more detailed and country-specific FIT policy design.