Netflix degrades the quality of the video it makes available to AT&T and Verizon, The Wall Street Journal confirmed, but doesn't do the same for T-Mobile and Sprint.

Netflix's concession supports last week's claim by T-Mobile CEO John Legere that Netflix's content is transmitted at a lower resolution over the networks of the two biggest U.S. carriers than over T-Mobile's network.

"Did you know that when you watch Netflix on T-Mobile you get it at 480p?" Legere asked during a video T-Mobile posted last week plugging its Binge On service. "And the duopoly is actually delivering your Netflix content at 360p. I'll bet you didn't know that. Go check; it's true."

Both Verizon and AT&T flatly denied throttling video content over their networks, and AT&T went so far as to say that "our customers on 4G LTE can get much higher resolution than T-Mobile's optimized 480p limit." Netflix failed to respond to multiple inquiries from FierceWireless over the last week regarding its policies for distributing content to mobile network operators.

The nation's two largest mobile carriers said they had no idea of Netflix's throttling practices until the news came to light. "We're outraged to learn that Netflix is apparently throttling video for their AT&T customers without their knowledge or consent," said Jim Ciccione, AT&T's senior vice president of external and legislative affairs, in a prepared statement.

Meanwhile, critics noted the policy appears to contradict Netflix's outspoken support of net neutrality principles. "Netflix fought hard during the open Internet proceeding to ensure that broadband providers could not engage in this same behavior that would benefit the same customers in the same way," Doug Brake of the Internet Technology and Innovation Foundation wrote in a blog post.

The Journal reported that Netflix admitted for the first time to capping its streams at 600 Kbps "to protect consumers from exceeding mobile data caps" that may lead to decreased viewing. The company cited "more consumer-friendly policies" of T-Mobile and Sprint, which slow network speeds rather than charging overage fees when users hit their monthly data allotments.

Netflix also said in a blog post that it plans to introduce a "data saver feature" in May to help users watch mobile video while minimizing their data consumption.

And while Legere's comments raised speculation that perhaps Verizon and AT&T requested lower-quality content from Netflix to ease the payload on their networks, both carriers denied those claims as well. "Verizon does not request any manipulation of content by the host service; a Verizon customer on-the-go gets the content at the resolution provided by the host service," a Verizon representative told FierceWireless Thursday.

Netflix's disclosure raises some complicated questions for the mobile industry as video consumption continues to ramp up, further congesting wireless networks. Carriers that charge overages when users blow past data limits may increasingly find they receive lower-quality content than competitors that merely throttle network speeds.

But it also highlights the fine line both carriers and content providers must walk when trying to deliver quality content while minimizing data payloads. There appears to be very little customer backlash from T-Mobile's Binge On, for instance, despite the fact that the carrier openly admits to "optimizing" – or degrading – the video quality for users of its service. Similarly, few – if any – users have balked at the inferior quality of Netflix's content over the networks of Verizon and T-Mobile. As data traffic continues to weigh down mobile networks, expect both operators and content providers to experiment with just how far they can go to minimize the data footprint.

For more:

- see this Netflix post

- see these FierceCable and FierceOnlineVideo articles

- see this Wall Street Journal report

Related articles:

Verizon, AT&T flatly deny Legere's claims that they provide lower-resolution Netflix video than T-Mobile

T-Mobile: Customers have watched 34 petabytes of video for no additional fee since Binge On launch

T-Mobile adds YouTube, adult content and more to Binge On

T-Mobile's Legere slams 'jerks' who question Binge On policies