New Zealand Prime Minister Jacinda Ardern and French President Emmanuel Macron announced the agreement at the United Nations as they and other leaders prepared for the UN general assembly this week.
Prime Minister Scott Morrison joined the two leaders and others at a meeting in New York on Monday on strategic responses to violent extremism.
"There should be no leave passes or different tolerances for different types of behaviour along the lines that exist in real space,"Mr Morrison said.
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"We cannot allow the internet to be weaponised by violent extremists."
Facebook chief operating officer Sheryl Sandberg has acknowledged the company did not take down videos of the Christchurch killings quickly enough and had to prevent the same occurring again.
The company removed 1.5 million copies of the video. It did this in 1.2 million cases where people had not yet seen the video. This suggested 300,00 people had seen the video before it was removed.