One thing to note is that the success of a mobile talk platform largely depends on how many people already use it. Albeit WhatsApp has hundreds of millions of users, many of them are outside the U.S. In fact, I only found a handful of users already on the service. Google Hangouts and Facebook Messenger are far more ubiquitous in the states. If you want to message U.S. friends, you may need to recruit them to the service.

However you won’t have to create an account with WhatsApp, the iPhone app offers to back up your media and messages on iCloud. If you migrate inbetween devices or reinstall the app, WhatsApp will conveniently prompt you to Restore Talk History. I also noticed that when reinstalling the app, I wasn’t prompted to confirm my device again. Convenient!

This no-account setup keeps WhatsApp light and effortless to use. It’s also an inherent security measure, since someone would have to spoof your phone number (or steal your phone) to impersonate you. I’ve seen other messaging platforms, such as the security centric Telegram Messenger , do the same thing. But it means that your WhatsApping is limited to a single device. You can enroll as many phones as you want, but your friends will need separate numbers for each listed in their address books. Facebook Messenger, on the other forearm, shoves all your messages among all your devices (and the Web) for maximum visibility. It also means you can’t just give an account to casual acquaintances—they will have your actual phone number. Fortunately, WhatsApp offers a Blocked Caller list.

But after so many years, WhatsApp is kicking off to feel a little stale. Facebook Messenger has a much cleaner, engaging design that I choose. I spend too much time tapping through menus to get to critical features in WhatsApp. Also, the Contacts section is misleading, since it makes no distinction inbetween who’s enrolled in WhatsApp and who isn’t; it just shows everyone I’ve saved to the Contacts app. The Favorites section shows your friends on the service, but you’ll want to prune this list, lest it become too long to be useful.

The core of WhatsApp is sending person-to-person messages, but you can also send group messages to a maximum of ten participants. These work as you’d expect: Messages sent to the group are filed in a special thread you can name, separate from other conversations. Participants can lightly unsubscribe and tweak their notifications, so no one has to feel spammed with group messages.

Alternatively, you can create a broadcast message. This functions a little like a blind carbon-copy. If you send a broadcast message to Alice, Bob, and Condoleezza, it emerges as if you sent the message directly to them. Broadcast messages show up threaded in recipients’ existing conversations with you, not in a separate thread as group messages do. It’s a bit confusing, but nevertheless a powerful communication instrument.

You can send more than text messages, too: photos, audio clips, movie clips (up to 16MB), and emojis are also options. You can fasten files, locations, and contact cards, too. Once, all of these were features hard to find outside WhatsApp, but they’ve since become commonplace. Noticeably missing are stickers, which have been adopted even by security-first services like Telegram and are (in my mind) the killer feature of Facebook Messenger.

WhatsApp began rolling out voice calls leisurely but sometimes demonstrated a phone icon even if the feature hadn’t been activated on your device. Instead of calling through WhatsApp, the call was placed using your existing voice plan and the built-in phone app. A cryptic error message was my only indication that my call wasn’t being routed through WhatsApp’s service. I last witnessed this problem almost a year ago, and it has hopefully been sorted out for all users now.

A year after voice launched, WhatsApp still doesn’t support live movie talking, a feature embraced by many modern messengers, including Skype, Google Hangouts, the ephemeral Snapchat, and Apple’s FaceTime. Snapchat, it should be noted, recently overhauled their voice, movie, and text talking interfaces and the practice is now vastly improved.

It took a while but you can now access your WhatsApp account through the Web—kind of. The feature very first spinned out for Android about a year ago and I assumed it would never make it to iPhone. To use it, you navigate to a special website and scan the QR code on the screen with a special reader in the WhatsApp Settings menu. This links your phone to the website, and you can send and receive messages from your computer.

Note that you are simply accessing the same account through your computer. We were astonished to detect that you can proceed to use the desktop app from your Manhattan office even when your phone is, for example, in Queens. However, if your phone loses connectivity, you won’t be able to use the desktop app. WhatsApp advises that you use a Wi-Fi connection when connecting to the desktop app to avoid searing through your data plan.

That switched for Android users in November two thousand fourteen when WhatsApp announced that it had partnered with WhisperSystems, the developers behind Signal , the excellent secure texting and talking for iPhone and Android. The two make a good pair, combining WhisperSystem’s extensive work on their open-source encryption protocol and WhatsApp’s enormous international user base. The practical upshot is that, according to WhisperSystems, "billions of encrypted messages are being exchanged daily."

This same security is now available to all WhatsApp users, regardless of platform. Best of all, messages sent inbetween platforms (from Android to iPhone, for example) are encrypted. All WhatsApp messages can now only be read by their intended recipients. No one, not even WhatsApp, can decrypt them. And not just messages: every photo, attachment, and even group message is secured end-to-end. The company manages to do this by letting each device manage its own encryption keys. If the FBI asked WhatsApp to mitt over someone’s talk logs, the most they would get would be unreadable mush.

WhatsApp also strives for ideal forward encryption and periodically switches the keys used to encrypt information. This means that if one message is successfully decrypted, that message’s key couldn’t be used to decrypt all previous or future messages. Editors’ Choice Wickr also employs a perfect-forward strategy and actually uses a different key for each and every message.

Unluckily, I had a mixed practice with encrypted talking on iPhone. By default, the app doesn’t tell you that your messages are being secured, however you can switch this. Instead, you tap on a user’s name and see a padlock on the following screen. But I encountered a situation where WhatsApp told me that my messages were encrypted end to end, but the app told my messages’ recipient that his connection was not encrypted. Were my messages secure or not? There’s no way to tell, and it doesn’t inspire accomplish confidence in WhatsApp’s security strategy. It’s unclear how end-to-end encryption works with WhatsApps desktop integration, and I have reached out to WhatsApp’s developers for clarification.

What’s Next for WhatsApp?