The partnership will allow Twitter to push furtherinto the sports world to attract new users now that the growth in its core business, an instant messaging platform, has slowed.

At the same time, the N.F.L. has recognized that more fans are forgoing traditional cable and satellite connections and relying primarily on the Internet to watch video.

The league also wants to maximize its revenue by selling the streaming rights to its games separately, a strategy that initially might have alarmed its traditional broadcast partners, who spend heavily for the right to show games over the air.