Facebook says it will begin requiring all games on its Web site to accept payments through its own currency system, Facebook Credits.

Developers will be able to use other currency systems, too, but they must accept credits. Those who accept only credits will get special incentives. The rule takes effect July 1.

Facebook gets a 30 percent cut when developers use credits to sell virtual goods and other items.

Deborah Liu, a platform marketing manager at Facebook, said in a blog post on Monday that more than 350 applications already use Facebook’s payment system. This accounts for more than 70 percent of all virtual goods transactions on Facebook.

Facebook users use virtual currency to buy items in popular games such as Zynga’s “FarmVille” and “Café World.”