Meta said today that the company plans to enable end-to-end encryption by default for Messenger by the end of this year. The tech giant is also expanding its test of end-to-end encryption features to “millions more people’s chats.”

The company has been building end-to-end encryption features in Messenger for years now. However, most of them have been optional or experimental. In 2016, Meta started rolling out end-to-end encryption protection through a “secret conversations” mode. In 2021, it introduced such an option for voice and video calls on the app. The company made a similar move to provide an end-to-end encryption option for group chats and calls in January 2022. In August 2022, Meta started testing end-to-end encryption for individual chats.

There is increasing pressure on Meta to enable end-to-end encryption so the company or others can’t access users’ chat messages. Protecting individual communications has become more important after a girl and her mother in Nebraska pleaded guilty to abortion charges in July after Meta handed over her DMs to cops. Last year, the police prosecuted the 17-year-old based on data about her direct messages from Messenger provided by Meta soon after the Supreme Court overturned the Roe. v Wade, a 1973 judgment to make abortion legal.

In a letter to the digital rights advocacy group Fight for the Future (via The Verge) earlier this month, Meta’s deputy privacy officer Rob Sherman said that it will roll out end-to-end encryption to Instagram DMs after the Messenger rollout. He also mentioned that “the testing phase has ended up being longer than we anticipated” because of engineering challenges.

In a blog post, the company explained that there were significant challenges in building out encryption features for Messenger. The company said had to shed the old server architecture and build a new way for people to manage their chat history through protections like a PIN.

Meta added that it had to rebuild over 100 features like showing link previews in conversations to accommodate end-to-end encryption. The company’s popular messaging app WhatsApp has had end-to-end encryption for years, and in recent years it has figured out a way to support multi devices for one account without breaking encryption. Meta said that the Messenger team is learning lessons from WhatsApp to implement end-to-end encryption.

After the incident, multiple organizations including Amnesty Internation, Access Now, and Fight for the Future wrote a petition to Meta and other platforms to enable end-to-end encryption for private chats.

Authorities around the world have been exploring rules that could put encryption in messaging apps at risk. While Meta has pushed back on these proposals through WhatsApp to support end-to-end encryption, it is yet to fully build out these protections for Messenger and Instagram DMs.