Fox had tested the format during the Teen Choice Awards.
AdAge notes that six-second spots are "all the rage" among digital video purveyors, especially given that historically much of the content did not carry ads.
Fox Sports said it would be offering advertisers on its sports programming the six-second ad format introduced by YouTube. In addition to the NFL, Fox is selling six second ads for the World Series and other events. TV networks have actually experimented with shorter ads in the past, but they never caught on.
"When the six-second ads are placed in unique positions, it has the potential to gain even more attention than a traditional unit."
"We have already been collaborating with brands and agencies that understand the need to evolve the model", Joe Marchese, Fox Networks Group's president of advertising revenue told Variety.
Fifteen-second spots have become more commonplace in recent years as networks and marketers work to find ways to get ad messages to viewers who are now accustomed to skipping through ad breaks via DVRs or watching on ad-free platforms such as Netflix. Now Fox hopes to make it a standard in the industry.
However, those units historically were sold as "splits" of longer-form inventory, bought by one multi-brand advertiser running shorter format ads for multiple brands.
And the average play lasts only four seconds - just two seconds shy of the new ads.
The move, which was first reported by the New York Times, comes after NFL Commissioner Roger Goodell said in March that speeding up games and changing the structure of commercial breaks was a priority.
While Fox has not disclosed explicit findings of its research, including the "Teen Choice Awards" six-second ad units, the National Football League rollout indicates that it is confident enough to place them in some of its highest-demand and most expensive inventory.