The third-party sign-up process is simple, but it may take some time before the feature is available to all users. Meta states that it can take up to three months for interoperability to be fully implemented after a messenger signs up.
In the first phase of interoperability, basic functions such as text messages, voice messages, images and files will be supported. Additional features such as video calls and group chats will follow in later phases.
It remains to be seen which messengers will ultimately choose interoperability with WhatsApp. So far, interest has been rather low, but this could change over time as the possibilities of cross-platform communication become increasingly important.
The original of this article first appeared at Schmidti’s blog