Smartphone apps like Angry Birds might seem harmless, but many are quietly tracking users’ locations, according to new research.

A team from Carnegie Mellon University looked at data from the 100 most popular apps in Google’s Android store to see which collect private information.

They published a list of the top 10 biggest surprises.

On top is the handy illuminating app Brightest Flashlight, which collects users’ locations and device IDs — a unique number that every smartphone has.

Research participants were “confused and surprised” by what they considered a violation of privacy, study leader Jason Hong, an associate professor at the university’s School of Computer Science, told the Daily News.

Popular app Angry Birds also tracks users’ locations and device IDs. Some apps collect data from users’ contact lists.

“A lot of people weren’t clear why the games needed [that information],” Hong said.

But there were “pleasant surprises” too, he said.

The Dictionary.com app, for example, collects location info so users can see what words people nearby are looking up.