"The events of Christchurch highlighted once again the urgent need for action and enhanced cooperation among the wide range of actors with influence over this issue, including governments, civil society, and online service providers, such as social media companies, to eliminate terrorist and violent extremist content online", stated the declaration made available to ET.
In addition to signing the Christchurch Call, Amazon, Facebook, Google, Twitter and Microsoft are publishing nine steps that they will take to address the abuse of technology to spread terrorist and violent extremist content.
Facebook has also announced new rules that it says would have prevented the gunman from livestreaming his March 15 act of terrorism. Anyone who commits one of several major infractions under Facebook rules-for example by linking to pro-terrorism propaganda-will now be banned from using Facebook Live for a period of time (such as 30 days) on the first offense.
In the 24 hours after the attacks, Facebook removed at least 1.2 million videos of the massacre as they were uploaded, but before they were viewed, according to Rosen.
It also said it would fund research at three universities on techniques to detect manipulated media, which Facebook's systems struggled to spot in the aftermath of the Christchurch attacks.
Woman faces murder count in death of man, 74, shoved off bus
The video shows the woman identified as Bishop, from two separate angles, shove Fournier off the bus using both hands. Investigators said Bishop left the scene with her child and did not offer assistance to the victim of her attack.
While the largest tech companies will be at the table, some of those responsible for running anonymous internet forums known for extreme content - such as 8 Chan and 4 Chan - are not taking part in the summit.
Representatives from Twitter and Google will be attending the meeting.
They promised investments in "digital fingerprinting" to track and remove harmful pictures and videos, and easy-to-use methods for users to report illicit content.
He added that Facebook had plans to extend these restrictions to other areas as well, including the ability to create ads on the platform.
Ms Ardern called the measures a "good first step".
The policy change comes in response to the Christchurch shooting in New Zealand, which was live-streamed on Facebook by its perpetrator.
"Companies like Facebook are becoming more aware and more willing to make reforms than the US, and they're doing it purely on grounds of public opinion", Knott said. While admitting that most countries already have laws governing such content, and most tech platforms already prohibit its sharing under their terms of usage, the proposal calls for closer cooperation between corporations, NGOs, and law enforcement, as well as between countries.
"The Christchurch Call will be assessed ultimately by the impact it has". In the wake of the violence in which 51 people were killed, New Zealand immediately imposed new gun control measures and introduced legislation that would ban most semi-automatic firearms.