The Prime Minister's Christchurch Call has triggered change before it's even started.

Facebook has announced a one-strike policy - to block people from using Facebook Live for set periods of time if they violate the platform's policies, such as by using terror propaganda in their profile.

The social media giant has also announced research into detecting manipulated media across images, video and audio.

Prime Minister Jacinda Ardern says it is a good first step to restrict terrorists using it as a tool.

She says new technology will be a major contributor to making social media safer, and stop the unintentional viewing of extremist content, and Facebook's actions show the Christchurch Call is being acted on.

It's a good early sign for the Prime Minister, who is likely keen to get a solid commitment out of this meeting, one communications expert says. 

Marianne Elliot told Heather du Plessis-Allen that the meeting is more narrow in focus than she would have liked, but in making it so limited Ardern will get some commitment out of those attending. 

"I think the pre-emptive action taken by Facebook is a good indication of the kind of concrete but relatively narrow commitment we will see. It's a step in the right direction from Facebook."

She thinks that we will see more social media sites doing similar moves, such as making it more difficult to load content. 

Elliot thinks that what Facebook has announced does not go far enough but action of any kind if still needed. 

• Facebook announces changes on eve of Christchurch Call
• Christchurch Call summit hours away from kicking off

"What this shows me is that these platforms are willing to take steps in the right direction when put under pressure from users and governments."