Mozilla kicked off its long-under-development plan to run ads in Firefox with the launch of version 33.1 on Monday.
The ads, which Mozilla calls "sponsored tiles," were first discussed by the company in February. In the months that followed, Mozilla defended the in-browser ad project against critics who called it a betrayal of the organization's philosophy, saying it was important to find other revenue sources besides its long-standing deals with search providers like Google.
Firefox 33.1, the special 10th anniversary edition released Monday, included the first instances of sponsored tiles. It followed the August introduction of the ads in Firefox's "Nightly" build, which is analogous to a pre-alpha edition.