The "Christchurch Call" was spearheaded by New Zealand's premier Jacinda Ardern and French leader Emmanuel Macron, who gathered tech executives and world leaders to launch the initiative at a meeting in Paris.
The call for change came after a gunman killed 51 people at two mosques in Christchurch in March while broadcasting his rampage live on Facebook via a head-mounted camera.
"The dissemination of such content online has adverse impacts on the human rights of the victims, on our collective security and on people all over the world," the signatories said in a statement.
Facebook in particular has faced withering criticism since the Christchurch attack, after the horrific footage was uploaded and shared millions of times despite efforts to remove it.
The social media giant, which participated in crafting the new commitments, said earlier on Wednesday that it would tighten access to its livestreaming feature.
Google and its YouTube unit also joined the pledge, along with Twitter, Wikipedia, Dailymotion and Microsoft. The companies said they would cooperate on finding new tools to identify and quickly remove extremist content.
"For the first time, governments, international organisations, companies and digital agencies have agreed on a series of measures and a long-term collaboration to make the internet safer," President Macron's office said in a statement.