More than 200 prominent women from around the world, including actors, journalists, musicians and former government leaders, have written an open letter urging CEOs of Facebook, Twitter, TikTok and Google to “prioritize the safety of women” on their platforms.

The letter was published Thursday by the World Wide Web Foundation and coincided with a pledge from the four tech giants to improve the safety of their online platforms. The companies’ vow and the letter, which seeks to hold them accountable to their promises, came on the second day of the U.N. Generation Equality Forum in Paris, which is focusing on gender equality.

The letter’s signers included Graça Machel, Nelson Mandela’s widow; Julia Gillard, the former prime minister of Australia; tennis champion Billie Jean King; and actors Thandiwe Newton, Ashley Judd and Emma Watson.

“The internet is the town square of the 21st century,” the letter said. “It is where debate takes place, communities are built, products are sold and reputations are made. But the scale of online abuse means that, for too many women, these digital town squares are unsafe. This is a threat to progress on gender equality.”

Diane Abbott, one of the signatories, who in 1987 became the first Black woman elected to the British Parliament, said she had faced unrelenting online harassment for years.

“There’s always been an undercurrent of racism and misogyny,” she said. “But social media has made everything so much worse. Every day you click on Twitter or Facebook, you have to steel yourself to see racist abuse — that’s a horrible feeling.”

Research by Amnesty International in 2018 looked into abuse against female politicians and journalists on Twitter in Britain and the United States. It found that Black women were 84% more likely than white women to be targeted by abusive tweets.

The commitments made by the tech companies Thursday — developed during a 14-month collaboration led by the foundation — would allow users to better manage who can engage with their posts and would strengthen the systems to report abuse. More than 120 experts from tech companies, civil society, academia and government in more than 35 countries worked on solutions to tackle online abuse.