There are a few key differences between the two most popular messaging apps, WhatsApp and Facebook Messenger. First, WhatsApp requires you to have an active phone number in order to create an account, while Facebook Messenger does not. This means that WhatsApp is better for staying in touch with people who you know only through their phone number, like family or friends who live far away. Secondly, WhatsApp offers end-to-end encryption by default for all conversations, meaning that only the sender and receiver can read the messages sent. Facebook Messenger offers end-to-end encryption as well, but it must be turned on for each conversation separately. Finally, WhatsApp allows you to send files of up to 100 MB in size, while Facebook Messenger limits file sizes to 25 MB.