The 26-year-old actress, who stars as Belle in the upcoming "Beauty and the Beast," said she found the courage to say no to selfies recently, reported Vanity Fair.
"For me, it's the difference between being able to have a life and not. If someone takes a photograph of me and posts it, within two seconds they've created a marker of exactly where I am within ten meters.
"They can see what I'm wearing and who I'm with. I just can't give that tracking data... Privacy for me is not an abstract idea," Watson said.
"I will sit here and answer every single Harry Potter fandom question you have but I just can't do a picture," she added.
The actress, however, finds it difficult to disappoint her young fans.
Watson said, "When am I a celebrity sighting versus when am I going to make someone's freakin' week? Children I don't say no to, for example.