Netflix has enforced a maximum limit on the quality of video streamed over AT&T and Verizon wireless networks for years, the company acknowledged Thursday. But Netflix also said it’s working on a way to give users control over how much bandwidth they wish to use to access the service.

The No. 1 subscription-streaming service said its default bit rate for viewing over mobile networks has been capped at 600 kilobits per second. That’s “in an effort to protect our members from overage charges when they exceed mobile-data caps,” according to a Netflix spokeswoman.

Netflix’s 600-Kbps limit for mobile video has been in place for more than five years, as first reported by the Wall Street Journal. The company caps video streams on AT&T and Verizon mobile networks, but does not for Sprint or T-Mobile because the latter two typically do not charge overage fees for exceeding data-usage limits.

“We’re outraged to learn that Netflix is apparently throttling video for their AT&T customers without their knowledge or consent,” Jim Cicconi, senior EVP of external and legislative affairs, said in an emailed statement.

That umbrage may stem from Netflix’s stance on network neutrality. The company has championed strong regulatory measures by the FCC to prevent Internet providers from blocking or degrading content delivered over their networks. But there’s nothing to prevent Netflix or other content providers from restricting their own services as they see fit.

According to Netflix, its practice of throttling mobile video hasn’t been an issue for customers. The company has a point, given that the streaming cap has been in place for several years without any hue and cry.

“Our research and testing indicates that many members worry about exceeding their mobile data cap, and don’t need the same resolution on their mobile phone as on a large-screen TV to enjoy shows and movies,” Netflix spokeswoman Anne Marie Squeo wrote in a blog post.

At the same time, Netflix expects to launch a “data saver” feature sometime in May. That will let customers set video bit-rate preferences for mobile usage, to dial it up to increase video quality if they have a generous and unlimited data plan or, conversely, set it lower to chew up less data. Netflix has allowed users to toggle video-quality settings for wireline broadband connections for some time.

“We recognize some members may be less sensitive to data caps or subscribe to mobile data plans from carriers that don’t levy penalties for exceeding caps,” Squeo wrote. “As we develop new technologies, we want to give all our members the choice to adjust their data-consumption settings based on their video preferences and sensitivity to their ISP’s data-overage charges.”