Tech giant Meta on Thursday was rolling out long-promised end-to-end encryption of chats and calls at Messenger and Facebook.

Ramped-up defenses against snooping that include disappearing messages come as the US company defends against lawsuits accusing it of being misleading about safety at its family of apps and of being a "breeding ground" for predators who target children.

Meta worked closely with outside experts, academics, advocates, and governments to identify risks and build mitigations "to ensure that privacy and safety go hand-in-hand," Messenger head Loredana Crisan said in a post.

Politicians and police agencies have opposed encrypting messages so that only senders and recipients can see them unscrambled, arguing that it protects criminals.

Privacy advocates, however, support better protecting conversations or exchanges online from those they are not intended for.

"We're thrilled that after years of investment and testing, we're able to launch a safer, more secure, and private service," Crisan said in the post, adding it is the biggest set of improvements to Messenger since the service launched in 2011.

End-to-end encryption will be on by default and come with the ability to edit messages or have them disappear 24 hours after being sent, according to Crisan.

The option to encrypt Messenger missives end-to-end has existed since 2016, but users had to turn it on.

People will still be able to report inappropriate messages to Meta, and the tech firm will notify users it if detects someone takes a screenshot of a disappearing message, according to Crisan.

More than 1.3 billion photos and videos are shared daily on Messenger, Meta said.

In total more than 40 US states are suing Meta, accusing it of putting profit ahead of the safety and well-being of users, particularly children.

Meta has fought back against such accusations.

The tech firm's fight against predators includes using sophisticated technology, employing child safety experts, reporting content to the National Center for Missing and Exploited Children, and sharing information with other companies and law enforcement agencies, a spokesperson told AFP.

Child victims of abuse online are a hot-button issue for regulators and tech companies are eager to show they are taking adequate measures to protect kids and teens.

Big tech companies, including Meta and Google, said last month they would team up in a new program called Lantern to fight online child sexual abuse or exploitation.