Mark Zuckerberg has lost a fifth of his net wealth, amid a violent and dramatic plunge in the price of Facebook’s shares.

The company announced overnight that its user growth and revenues had missed expectations.

Investors disappointed in the news immediately sold shares, sending the price of the stock plunging by 20 per cent.

Mr Zuckerberg said during the announcement that the problems were caused by a variety of issues, including new investment into security and data regulation.

Facebook’s monthly active user count was 2.23 billion, slightly behind the 2.25 billion forecast by analysts.

How to stop Facebook from revealing everything about you Show all 9 1 /9 How to stop Facebook from revealing everything about you How to stop Facebook from revealing everything about you Lock your profile down If you haven’t done this already, do it now. In Settings, hit the Privacy tab. From here, you can control who gets to see your future posts and friends list. Choose from Public, Friends, Only Me and Custom in the dropdown menu. How to stop Facebook from revealing everything about you Limit old posts Annoyingly, changing this has no effect on who’s able to see your past Facebook posts. Instead, on the Privacy page, you have to click on Limit Past Posts, then select Limit Old Posts and finally hit Confirm on the pop-up. How to stop Facebook from revealing everything about you Make yourself harder to find You can stop completely random people from adding you by selecting Friends of Friends from the dropdown menu in the Who can send you friend requests? section of the Privacy page. It’s also worth limiting who can find your Facebook profile with your number and email address. At the bottom of the page is the option to prevent search engines outside of Facebook from linking to your profile. How to stop Facebook from revealing everything about you Control access to your Timeline You can limit who gets to post things on your Timeline and who gets to see posts on your Timeline too. In Settings, go to Timeline and Tagging and edit the sections you want to lock down. How to stop Facebook from revealing everything about you Block people When you block someone, they won’t be able to see things you post on your Timeline, tag you, invite you to events or groups, start conversations with you or add you as a friend. To do it, go to Settings and Blocking. Annoyingly, you have to block people on Messenger separately. You can also add friends to your Restricted list here, which means they’ll still be friends with you but will only be able to see your public posts and things you share on a mutual friend's Timeline. How to stop Facebook from revealing everything about you Review tags One of Facebook’s handiest privacy features is the ability to review posts you’re tagged in before they appear on your Timeline. They’ll still be visible on the News Feed while they’re fresh, but won’t be tied to your profile forever. In Timeline and Tagging, enable Timeline review controls. How to stop Facebook from revealing everything about you Clean up your apps You can view a list of all of the apps you’ve connected to your Facebook account by going to Settings and Apps. The list might be longer than you expected it to be. It’s worth tidying this up to ensure things you no longer use lose access to your personal information. If you don’t want to log into websites and apps with your facebook account, scroll down and turn Platform off. How to stop Facebook from revealing everything about you Change your ad preferences You can view a list of everything Facebook thinks you’re into and tinker with your ad preferences by going to Settings and Adverts. A lot more information is displayed on the desktop site than the app, so we’d recommend doing this on a computer. How to stop Facebook from revealing everything about you Download your data Facebook lets you download all of the data it has on you, including the posts you’ve shared, your messages and photos, ads you’ve clicked on and even the IP addresses that are logged when you log in or out of the site. It’s a hell of a lot of information, which you should download to ensure you never over-share on the social network again.

Although Facebook’s monthly active users were up 11 per cent year-on-year, growth had fallen flat in the US and Europe, its key advertising markets. Europe’s fall was partly down to the rollout of GDPR, the company told investors.

Revenue estimates also fell short, reaching $13.3bn, as the company continues to deal with fake news and privacy issues in the wake of the Cambridge Analytica scandal by investing in improved security controls.

“As I’ve said on past calls, we’re investing so much in security that it will significantly impact our profitability,” CEO Mark Zuckerberg said in an earnings call.

“We’re starting to see that this quarter.”

Facebook warned investors that it expected revenue gains to slow down because of users utilising options to limit advertising on the social network.

“Our total revenue growth rate decelerated approximately seven percentage points in Q2 compared to Q1,” warned chief financial officer David Wehner.

“Our total revenue growth rates will continue to decelerate in the second half of 2018, and we expect our revenue growth rates to decline by high single-digit percentages from prior quarters sequentially in both Q3 and Q4.”

Some analysts have also put the fall down to social media reaching its peak.

“Teens are abandoning – or just not joining the site – as ‘oldies’ migrate there,” said Richard Holway, chairman at UK tech analyst house TechMarketView.

“Teens have been moving to Instagram, WhatsApp and Messenger. But now it looks as if overall usage is stalling.

“Indeed, daily and monthly users in Europe actually fell for the first time ever in Q2. GDPR undoubtedly played a part here.”

One area Facebook had reason to celebrate was in its other platforms, especially Instagram, which reached a milestone of one billion active years this quarter.

“We believe Instagram has been able to use Facebook’s infrastructure to grow more than twice as quickly as it would have on its own,” Mr Zuckerberg said.

“I’m really excited about video too, and this quarter we launched IGTV.

“People are watching less TV but more video, but most video is not yet optimised for mobile. IGTV will help solve that problem.”