WhatsApp rivals have recorded a surge in new users after a mass outage took the Facebook-owned messaging service offline for six hours on Monday.

Signal, a messaging tool that offers heightened privacy features, said “millions of new people” had download its app in the wake of the blackout.

Meanwhile Telegram, another encrypted messaging app, surged up the iPhone download charts to take the number one spot in the US.

Facebook was forced to apologise after a faulty update knocked out all of its apps for hours last night. Its website as well as the Messenger app, Instagram and WhatsApp all failed for nearly 3bn users.

WhatsApp is the world’s most popular mobile messaging app with an estimated 2bn users, offering encrypted text messaging as well as audio and video calls.

Signal has been endorsed by whistleblowers such as Edward Snowden as well as Jack Dorsey, the Twitter boss, and is run as a not-for-profit. 

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The app is backed by $50m from Brian Acton, one of the founders of WhatsApp who quit Facebook in 2017. It has more than 50m downloads on Google’s Android phones.

Telegram, an encrypted messaging service which has 1bn downloads, jumped from number 55 on the Apple App Store chart in the US to number one in messaging. 

The app was founded by Russian internet entrepreneur Pavel Durov, who fled the country after coming under pressure from the Kremlin. The app has proved popular among dissidents.

Encrypted messaging services have been criticised for making it harder for authorities to track down criminals and block illegal content.

Facebook outages

Network experts attributed the problem to Facebook’s own servers being unable to connect to the global “Domain Name System” used to direct internet traffic. 

Facebook said that “configuration changes” it was making to its backbone servers accidentally disconnected its technology from the rest of the web.

Cloudflare, an internet infrastructure provider, said: “It was as if someone had ‘pulled the cables’ from their data centres all at once.” 

The problem also affected Facebook’s own workplace messaging systems, emails and even door access systems, which all ran on the company’s internal network.