The site "Nous Toutes ." (We are all harassed) aims to collect accounts of incidents "in the street, at work, in the private sphere" Marie Laguerre, 22, said.
"It's anonymous, and that will allow these women to talk freely," she added.
Laguerre, a student, wrote on Facebook last week that she was returning home when a man started making lewd comments. She told him to "shut up" and kept walking away, while the man went in the opposite direction.
In surveillance video provided by the cafe, the man is then seen grabbing an ashtray from a table on the cafe's patio and throwing it at her.
He then returns and strikes Laguerre across the face.
She filed a complaint with police and later posted the video, writing that "we must no longer keep quiet".
Since her video went up on Facebook, Laguerre has received messages from around the world from women sharing their own experiences as well as from men offering their support.
Laguerre has done the rounds of French and international media retelling her story but now wants to capitalise on her new high-profile "to deliver a message and improve things".
Such harassment is a worldwide problem, she said.
Laguerre contacted established women's groups for advice, said Fatima Benomar, spokeswoman for one such organisation "Les Effrontees".
"We considered things together and came up with the idea to creat this site," she added.
The messages from the online witnesses will also go up on Facebook.
Similar online projects already exist, but Laguerre said it was "important" to her to start a new initiative to tackle the problem.
Paris prosecutors have opened an inquiry following the posting of the video of the assault on her, according to legal sources.