WhatsApp is probably the most popular IM client on a global scale. WhatsApp is owned by Meta (parent company of Facebook), which is a turn-off for some people. However, this does not deter most people. With that in mind, and the fact I have international contacts, I keep WhatsApp for that reason alone. However, no international friend is close enough to where we are communicating daily, so the app is probably not as important to me as it will be for others.