Verizon Communications Inc. has admitted to throttling video streaming speeds after its customers complained that speed tests on Netflix seemed to indicate a cap at 10 megabits per second.

At a time when net neutrality rules, the idea that Internet service providers shouldn’t limit delivery of content, could be kicked to the curb, throttling speeds is something of a sensitive matter. YouTube users have also complained of slow speeds and some have switched to using virtual private networks.

Verizon acknowledged throttling Netflix content to both ArsTechnica and The Verge, but said the slowdown was related to optimizing video.

“We’ve been doing network testing over the past few days to optimize the performance of video applications on our network,” said a spokesperson from Verizon. “The testing should be completed shortly. The customer video experience was not affected.”

Verizon said no application in particular was targeted, and the testing it was doing was applied all over the network. The issue remains though that capping speeds is essentially “throttling” even when its dressed-up as video optimization.

Although Netflix Inc. says for Ultra HD quality video, users need speeds of about 25 Mbps, 10 Mbp should be sufficient for most users watching standard HD video. As for YouTube, users were right to question if Verizon was “manipulating” speeds. A thread on Reddit indicates that users weren’t only annoyed about the slowdown and resulting buffering of content, but the “silent” manner in which Verizon did it.

Again, Verizon said that no specific service had been targeted when asked about YouTube speeds. “We’re always looking for ways to optimize our network without impacting our customers’ experience,” a spokesperson told ArsTechnica. To quell fears that Verizon might be favoring its own services, the company also said that its own Go90 video streaming app had been affected by the test.

The testing may well be innocuous. But as the Federal Communications Commission moves closer to undoing net neutrality rules that seem to be favored by few except the agency and Internet service providers, silently slowing down speeds is bound to meet with some amount of scrutiny.

Image: Teppo Kotirinta via Flickr