The report button had already been introduced for mobile phone users, but is now available across all platforms, including desktop websites, The Independent reported.
The move has been hailed by the hundreds of thousands of campaigners who had called for the social network sites to take action against threatening and abusive users.
Criado Perez, from north London, was one of a number of women who were subjected to a torrent of abuse by Twitter users last month.
Perez successfully lobbied to keep women on the face of bank notes, but then began receiving rape threats from various users for 48-hours.
Classicist and television historian Professor Mary Beard, Guardian columnist Hadley Freeman, Independent columnist Grace Dent and Europe editor of Time magazine Catherine Mayer were also then targeted along with a number of other women.
They received bomb threats, while two of them were warned they would be raped by users of the site.
The threats led to a public outcry for action from the microblogging site to introduce measures that would protect users.
Perez said it was "great" that Twitter has listened.
"There are still issues: users have to agree for the report to be potentially shared with the harasser, and there are some boxes that could be auto-populated that aren't. But overall, this is a fantastic first step," she was quoted by the daily as saying.