AT&T is now exempting DirecTV streaming video from data caps on AT&T's mobile Internet service.

AT&T purchased DirecTV in July 2015 and today pushed an update to the DirecTV iPhone app to implement the data cap exemption. "Now you can stream DirecTV on your devices, anywhere—without using your data. Now with AT&T," the app's update notes say under the heading "Data Free TV." This feature requires subscriptions to DirecTV and AT&T wireless data services.

It sounds like the data cap exemption may not apply to all data downloaded by the app, as the update notes further say that "Exclusions apply & may incur data usage." The service is also "Subject to network management, including speed reduction." We've asked AT&T for more information and will provide an update if we receive one.

The iPhone update also lets customers download shows from their home DVR to mobile devices. The DirecTV apps for Android and iPad have not yet received the update. (UPDATE: It's now available on iPad.)

Data cap exemptions—also known as zero-rating—are controversial and are being reviewed by the Federal Communications Commission. The FCC's net neutrality rules prevent ISPs and mobile carriers from speeding up online services in exchange for payment, but they don't include a specific ban on zero-rating. Instead, the net neutrality regime has the FCC review zero-rating on a case-by-case basis to determine whether specific implementations harm customers or competitors.

When granting AT&T's acquisition of DirecTV, the FCC barred AT&T from exempting its own online video services from home Internet data caps that are applied to competitors. AT&T argued against the condition, which does not apply to mobile Internet data caps.

While DirecTV will no longer count against AT&T data caps, Netflix and other video services will still use up customers' data allotments unless the companies delivering online video pay AT&T to bypass the caps. AT&T started charging businesses for data cap exemptions in January 2014.

The FCC began reviewing zero-rating implementations from Comcast, AT&T, and T-Mobile in December 2015, but it hasn't yet made any decisions. Since that review began, Verizon Wireless started exempting its own video service from data caps, while counting data from competitors such as YouTube and Netflix against customers' caps.

Even before today, AT&T was getting creative with data caps since purchasing DirecTV, with promotions that encourage customers to subscribe to pay-TV service. AT&T's unlimited smartphone data plan is only available to people who also subscribe to DirecTV or U-verse TV. (There are still cheaper plans with data caps, which will benefit from the DirecTV zero-rating).

AT&T also provides unlimited home Internet data to customers who bundle AT&T Internet with TV while imposing data caps on other home Internet subscribers. This effectively makes it harder for subscribers to go Internet-only and watch online streaming services instead of cable or satellite TV. Internet-only subscribers have to pay an extra $30 a month for unlimited data on their AT&T home Internet connections.

UPDATE: AT&T has formally announced the DirecTV zero-rating in a blog post, which says video will also be zero-rated in the U-verse app.

AT&T also answered some of our questions. "We are not treating our services differently from any other data," AT&T told Ars. "Other content providers can do the same thing through our sponsored data program."

DirecTV is apparently "paying" AT&T to participate in the sponsored data program, though this is simply money being transferred from a subsidiary to its owner. "Unaffiliated third parties are free to participate in that program as well," AT&T said. "Our sponsored data program is available to any interested content provider."