Mark Zuckerberg criticized iMessage on Monday for not working with Android smartphones.
He tweeted a snapshot of a Facebook billboard ad that laughs about iMessage's green Android bubbles and blue iPhone bubbles.
"WhatsApp is significantly more private and secure than iMessage, with end-to-end encryption that works across iPhones and Android," Zuckerberg said on Instagram.
Some users have long complained about cross-device messaging, poor-quality compressed videos, the absence of read receipts, group text issues, and misplaced emoticons.
Google criticized Apple early this year, using an unusual search bar placement.
Google claimed Apple turns iPhone and Android text communications into SMS and MMS, which are decades-old systems.
Google prefers Apple utilize RCS. Tim Cook has avoided making iMessage compatible with Android phones since it helps sell iPhones.