Transcript for Apps that could be tracking shopping habits
Back now with "Gma's" retail revolution and so many of us use our phones to shop and now recent study from princeton and Berkeley reveries that as many as 70% of smartphone apps track users meaning all that saving you're doing on time and money may be costing you your privacy. ABC's Becky Worley has the details. Reporter: Have you ever received a notification on your phone from one of your favorite brands that seems ridiculously well timed? All of a sudden the gap will pop up on my phone stating I have a coupon and can go shopping. Referee time. Every time I go there. Do you ever get ads on your phone that seem to know where you are. Oh, absolutely. Reporter: He says the urban outfitters app has his number. Whenever I come within like 50 feet, I get like, hey, did you know there's this sale ending in a couple of days. Reporter: It's not just a coincidence, shopping apps from companies like Macy's and urban outfitters use the phone's gps to access your location. They have technologies that can follow you as you walk through sectors of the store and connect to your data so they know who you are. Reporter: Sure enough, after I installed the urban outfitters app it pings me as I walk into a store in Philadelphia. In San Francisco, it was almost a block away when the app lit my phone up with notifications. It makes sense, their best chance to get me into the store is when I'm close by. The Macy's notifications were even more interesting. They pinged me once when I entered their store in Philadelphia. I just put my hand on the door handle and a notification popped up saying welcome to Macy's. They know I'm here. Then again in San Francisco two timely notifications, not in a Macy's store but get this, while I was in other stores. They sent me a 30% off notification while I was in this store, one of their direct competitors. They also pinged me while I was in a small independent boutique. Literally in the dressing room. In addition to gps stores are using bluetooth, wi-fi and even your phone's microphone to let them know where you are. And then selectively target you with ads. Retailers hoping to keep your money in their stores and off the internet. Make stores into the internet. Yeah, essentially be able to track people in stores like we track people online and then connect the two. Now, Michael, Macy's told us they only send relevant store information to those who have opted in when they're geographically near a Macy's store. For some that's still giving them too much information? A little too much information. Show of hand, how many audience members use a retail app? Quite a few. By another show of hands how many of you are creeped out they're tracking your location? Everybody. The good news, can you turn that off. Let me show you. You go to settings on your phone and then you scroll down to privacy and make it straightforward. Location services is the top one here and look at all these shopping apps. Macy's always using -- Is that your phone? I have a lot of apps. You do a lot of shopping. You can turn it off. I do a lot of shopping. None of my business. I am a consumer reporter. I have to consume. You turn these apps off. Never. It depends what you like. Some like the appreciation of getting a coupon. They like a deal and coupons. I will keep researching this and do more shopping. You got all the apps for it. Thank you, thank you Becky. We really appreciate that. More information on how to turn off location tracking for both iPhones and androids and that's on our website and we're going
This transcript has been automatically generated and may not be 100% accurate.