Key points: Most widely used messaging app Uses the same encryption protocol as Signal Collects heaps of your data Free, but owned and operated by Meta WhatsApp is the most popular private messaging app on this list, with about 2 billion monthly users, according to Exploding Topics. Because it's so popular, there's a higher chance that other people you might be chatting with have WhatsApp, and therefore your chats can be encrypted. And if the person you're chatting with doesn't have WhatsApp -- or any of the other messaging apps on this list -- then your messages might not be encrypted. WhatsApp uses Signal's encryption protocol, so your chats and calls are just as end-to-end encrypted as those on Signal. But the main distinction between Signal and WhatsApp is that the latter collects loads more user data, even compared to Telegram. According to WhatsApp, it automatically collects information like your usage and log information, device and connection information, location information and cookies from you when you use the app. And other people on the app can provide WhatsApp with information about you, too. "When other users you know use our Services, they may provide your phone number, name, and other information (like information from their mobile address book) just as you may provide theirs," WhatsApp writes in its privacy policy. That means even if you don't use the app much and only use it to chat with a friend or relative overseas every few months, your data can still end up in WhatsApp's hands via your friend or relative. I guess the fact that the app collects so much data on you shouldn't be a surprise, considering the app is owned by Meta. The Federal Trade Commission filed a report in 2024 that said Meta and other companies collect and retain "troves of data, including information from data brokers and about both users and nonusers of their platforms." "These surveillance practices can endanger people's privacy, threaten their freedoms and expose them to a host of harms, from identity theft to stalking," then-FTC Chair Lina Khan wrote. Some people have expressed concerns about WhatsApp's data security. In 2024, The Intercept reported that governments may be able to take advantage of the limitations of secure messaging apps by performing traffic analysis -- but this is a limitation of many messaging apps, not a vulnerability of WhatsApp specifically. In 2023, CyberNews reported that the phone numbers of close to 500 million WhatsApp users had been leaked. However, the Check Point Research team could not prove the numbers are from WhatsApp users. "WhatsApp has no backdoors and we have no evidence of vulnerabilities in how WhatsApp works," a WhatsApp spokesperson told CNET in an email. "We have a proven track record addressing issues we identify and have worked to hold bad actors accountable. We have the best engineers in the world proactively looking to further harden our systems against any future threats and we will continue to do so." The spokesperson also said WhatsApp doesn't keep logs of who people message or call. Again, there is no such thing as a perfectly secure app, but those are some alarming stories paired with how much data WhatsApp could collect on you. So while your messages might be secure and unreadable to anyone besides their intended recipient, the data WhatsApp collects on you is a veritable treasure trove of information others are out to get. Despite the data collection, WhatsApp is still the world's most popular encrypted messaging app. So, if the person you want to talk to has WhatsApp and an unsecured message app, you should try to convince them to use Signal. You can download WhatsApp from Apple's App Store or the Google Play store for free.