Japan-based Line is finally bringing end-to-end encryption to its mobile messaging service, which is used by over 211 million people worldwide each month.

The company said today that a new security feature, dubbed ‘Letter Sealing’, will bring encryption to messages and features on the service, starting with one-on-one chats and the service’s location-sharing feature, on its mobile and desktop apps.

“This method of secure communication facilitates uncrackable encryption by scrambling the chat content with a key, which is stored only in user device instead of a centralized server. With the advanced security system, it is technically impossible for the chat content to be disclosed in the server or to a third party,” Line said in a statement.

The feature is only activated when all parties interacting have it present on their device. Initially, users must switch on encryption themselves — the setting is buried inside menus — which could impact the initial rollout. But Line plans to switch it on by default for all users soon, initially it is only default for those with one Android device registered to their account. There are plans to add encrypted sealing to Line for desktop and other operating systems over time, too.

Still, the move is a much needed one. A number of Line’s messaging rivals have already embraced end-to-end encryption, including WhatsApp, Apple’s iMessage, and Telegram. Line did add an encrypted chat option last year, but it requires users to open a different kind of chat window, which almost certainly means it is not widely used.

Line has previously denied claims that it shares user data with the government in Thailand, its second largest market with over 30 million users. Adding end-to-end encryption should help the company argue that keeps data locked up, secure, and out of the hands of third parties.

It’s worth adding that, while this news looks good on paper, members of the security community are yet to have a go at disproving the security.