Facebook CEO Mark Zuckerberg Congress Testimony: Key Quotes

Facebook chief Mark Zuckerberg appeared before US lawmakers Tuesday to apologise for how his company has handled the growing furore over online privacy, to promise change, and explain the social media giant's policies.

The wide-ranging questions - including about Cambridge Analytica, which used data scraped from 87 million Facebook users to target political ads ahead of the 2016 US election - put the 33-year-old billionaire under a microscope for several hours at a joint Senate committee hearing.

Here are top quotes from Zuckerberg, and some of the dozens of senators who grilled him.

How to Check If Your Facebook Data Was Shared With Cambridge Analytica

Setting things straight
"We didn't take a broad enough view of our responsibility, and that was a big mistake. And it was my mistake, and I'm sorry. I started Facebook, I run it, and I'm responsible for what happens here."

"When we heard back from Cambridge Analytica that they had told us that they weren't using the data and deleted it, we considered it a closed case. In retrospect, that was clearly a mistake. We shouldn't have taken their word for it. We've updated our policy to make sure we don't make that mistake again."

"It will take some time to work through all the changes we need to make across the company. I'm committed to getting this right. This includes the basic responsibility of protecting people's information, which we failed to do with Cambridge Analytica."

"We're investigating every single app that had access to a large amount of information in the past. And if we find that someone improperly used data, we're going to ban them from Facebook and tell everyone affected.

Russian alarm
"One of my greatest regrets in running the company is that we were slow in identifying the Russian information operations in 2016."

"There are people in Russia whose job it is to try to exploit our systems and other internet systems.... So this is an arms race. They're going to keep getting better and we need to invest in getting better at this too."

Trump and special counsel
Asked if Facebook executives have been interviewed by special counsel Robert Mueller, who is investigating Russian interference in the US election: "Our work with the special counsel is confidential.... I actually am not aware of a subpoena. I believe there may be, but I know we're working with them."

"I know we did help out the Trump campaign overall in sales support in the same way we do with other campaigns."

Challenges ahead
"There will always be a version of Facebook that is free."

"We need to take a more active view in policing the ecosystem and watching and looking out and making sure that all the members in our community are using these tools in a way that's going to be good and healthy."

Asked if he believes the social media giant, with over two billion users worldwide, amounts to a monopoly: "It certainly doesn't feel like that to me."

Right to privacy
Senator Dick Durbin: "Would you be comfortable sharing with us the name of the hotel you stayed in last night? If you messaged anybody this week, would you share with us the names of the people you've messaged?"

Zuckerberg: "Senator, no I would probably not choose to do that publicly here."

Durbin: "I think that may be what this is all about: your right to privacy, the limits of your right to privacy, and how much you give away in modern America in the name of connecting people around the world."

Pressure is on
Senator John Thune: "This should be a wake-up call for the tech community.... We're listening, America is listening, and quite possibly the world is listening too."

Senator Bill Nelson: "Let me just cut to the chase. If you and other social media companies do not get your act in order, none of us are going to have any privacy anymore."