(CNN)"Hey girl! Are you alone?"
"I'm gonna come back for you later."
"It'll be so good, you won't want to call it rape."
These are the kinds of catcalls that women -- and some men -- endure on the streets of the world's cities every day.
The problem is widespread. A 2014 study found that in the UK, for example, 90% of women say they experienced their first street harassment before turning 17. More than 70% of South African women say they have been followed by men on the street. Almost half the women surveyed in India say someone has exposed themselves to them.
So women around the world are fighting back. They're documenting actual catcalls they've received by writing them in chalk on streets and sidewalks from Boston to Barcelona, then posting them to Instagram.
What began in 2016 with a single account, Catcalls of NYC, has become an international movement against street harassment. There are now more than 70 related Instagram accounts around the world where people share photos of pavements they've chalked with the words they've had to endure.
"All of the catcalls I post are submissions that have been made to real people in public spaces, most of the time the street, occasionally on public transportation such as buses and trains," said Farah Benis, who founded Catcalls of London.
Organizers of the movement hope the messages -- many of them startlingly crude -- call attention to a global problem.
It's one thing to hear a catcall. It's another thing to see a catcall, tattooed in neon chalk on the spot where the harassment actually happened.
Here's a look at some of them.
Ciudad Obregón, Mexico
The movement was inspired by a university class
Sophie Sandberg, a senior at NYU, started Catcalls of NYC three years ago.
"I had a writing class assignment which inspired this project," said the student, now 22.
Since then the account has posted more than 350 examples of New York catcalls and attracted 119,000 followers.
"Women have stopped me on the street to thank me for the project," she said. "I think it really helps people after they've been harassed to have somewhere to go and simply share what happened to them. That's what the Instagram account does."
It's also inspired grassroots activists such as Benis, 32, a startup consultant who launched Catcalls of London in late 2017. It now has almost 5,000 followers. Dozens of other cities have since followed suit.
The photos have sparked a range of reactions
Last month the two women launched www.chalkback.org to provide an online community and help others start a Catcalls account in their own city.
People of both genders "have been shocked by the vulgarity of some comments," Sandberg said.
"I've had men say that catcalling is free speech, or that it's a compliment. I've also had men say thank you for the account -- because it's allowed them to become educated about what's going on (many of them aren't aware of how widespread catcalling is). I've also had men ask me how they can help."
Taken together, the bold scribblings on dull pavements paint an alarming message: These words are creepy, these words instill fear. These words are common.
"By creating awareness of street harassment, I hope we can have more people involved in the solution," Sandberg said. "More people who know about this behavior can look out for it and hopefully make the streets safer for everyone."