When the website for David Choffnes’ app Wehe went down last week, his student thought the web servers were under attack.

“Then we realized that we were just featured at the top of Reddit,” said Choffnes, assistant professor in Northeastern’s College of Computer and Information Science.

Wehe is a mobile app that can detect when an internet service provider is violating net neutrality—for example, when ISPs treat certain Internet data sources more favorably than others. The Federal Communications Commission recently repealed net neutrality, despite widespread consumer objection. Choffnes developed the app with help from his students, Fanfang Li, who is earning his doctorate in computer science, and Kirill Voloshin, CS’ 18.

Even before the repeal, Choffnes’ research has found that ISPs will throttle—that is, reduce the available bandwidth—certain apps, like those that provide video streaming. “That’s a textbook example of violating net neutrality, because you are treating some applications differently than others,” Choffnes said.

Wehe was released in 2015 for Android devices. But when Choffnes tried to make the app available for iPhone users last month, Apple wouldn’t allow it in its App Store, citing several reasons that Choffnes said didn’t make sense. First, the Apple reviewer falsely claimed Wehe was an app to test internet download speeds.

“But that’s not what it is,” Choffnes said, explaining that he has presented the published, peer-reviewed research behind Wehe at top publication venues, including the Internet Measurement Conference. The app measures whether an ISP is enabling some apps to perform better than others, not the maximum download speed that the ISP supports. “I wasn’t going to be deceptive and call it a speed test when it isn’t.”

The second reason Apple listed was that Wehe appeared to bring no value to users. “I just thought that stung a little,” Choffnes said, tongue firmly in cheek. “That seemed like a personal jab.”

Disappointed, Choffnes shared his experience on Twitter. A reporter from Motherboard took notice, reached out to Choffnes, and wrote an article about the debacle, which quickly gained traction on Reddit. A representative from Apple called Choffnes spontaneously that same day.

“They asked me again to resupply all the information about how the app works and the technical documentation—which is to say the scientifically peer-reviewed papers—and that they would escalate it and get back to me,” Choffnes said. “Within 18 hours of that call, they had approved the app and it’s now in the store.”

As a result of all the buzz, people flocked to the App Store to download Wehe.

“For the better part of a day, my team and I were scaling out our servers so we could handle the load,” Choffnes said. “We got over 60,000 successful tests on the app from around the world just in the first day since that Motherboard article came out.”

The more app users, the better. In addition to being a test of net neutrality for consumers, Wehe is a research tool for Choffnes and his team. The data the app collects provides a global view of how ISPs around the world are operating in relation to net neutrality.

Choffnes is interested in learning which networks are throttling, what apps they slow down, and what unintended consequences may arise. For example, throttling certain video streaming apps can cause a blurry picture, long buffering delays, and negatively impact the user experience. And arbitrarily slowing down certain apps but not others can create the opportunity for “winner and losers,” Choffnes said.

“You can have some apps that are able to stream to their users at really high resolution, and that might make them look better than their competitors that are throttled in a way that requires a lower resolution,” Choffnes said. “That’s one of the main issues with doing throttling that impacts a specific category of Internet traffic as opposed to doing it equally for everybody.”