A new kind of advertising is coming to N.F.L. games and other programming on Fox Sports this fall: the six-second television commercial. Fox Networks Group will offer the bite-size slots alongside its standard 15- and 30-second ads for a variety of sporting events after first testing the format on its broadcast of the Teen Choice Awards in mid-August. People are used to seeing short video ads on platforms like Snapchat, Facebook and YouTube, but not so much on network TV, where the currency for decades has been 15- and 30-second ads. While TV networks have experimented with shorter commercials in the past, largely as publicity stunts for specific brands, Fox is hoping to make six-second ads an industry standard across broadcasters as consumers in the internet era show less tolerance for frequent, bloated ad breaks during shows.