iMessage is great, but most of its functionality (including free messages) only works if you're messaging other iPhone and iPad users. That means if you ever need to message someone on an Android device, you're stuck sending a plain old SMS - and paying for it.

Luckily, there are loads of other messaging apps around that work across platforms, letting you message friends and family across loads of devices for free, and sometimes even with encryption included to keep what you send safe from prying eyes.

WhatsApp

WhatsApp

Free
Get from the App Store.

One of the most popular messaging apps is WhatsApp, which allows you to send messages, videos, pictures, audio, links and even locations to your friends or family for free over WiFi or using your data allowance if you're on 3G or 4G at the time.

Whatsapp is easy to use and works across Android, iOS and even in web browsers. You can message individual contacts or create a group message with a particular set of friends, for example.

Facebook Messenger

Facebook Messenger

Free
Get from the App Store.

Facebook Messenger is similar in many ways to Whatsapp (in fact, Facebook actually owns Whatsapp).

Using Facebook Messenger, you'll be able to send messages, videos, pictures, links and more to your Facebook friends or Facebook pages within the app. You can start group chats or have individual conversations, and there are plenty of stickers and gifs available to send too.

There are also games to play within Messenger and a new Messenger Day feature that's similar to Snapchat and Instagram Stories.

Google Allo

Google Allo

Free
Get it from the App Store

The newest messaging service on this list, Google Allo is the company's attempt to move iOS (and Android) users to a universal platform for messaging akin to WhatsApp or iMessage.

It's a good option if you want the multimedia options afforded by iMessage but want to message across platforms. True, WhatsApp or Viber do this, but Allo offers Google Assistant, a text based bot that helps you by answering your queries. You can chat to it directly, or bring up intelligent search options in conversations with others by starting your message '@google'. 

It will only work on your phone though because it needs to be associated with your phone number - so no Allo on iPad or Mac.

Snapchat

Snapchat

Free
Get from the App Store

Snapchat is currently taking the world by storm. It's different from Facebook Messenger and Whatsapp in that its messages are temporary, expiring after they've been viewed. It's great fun, although not entirely practical if you want to share important information or organise a get-together.

There are new features cropping up in Snapchat every day, though, so it's always fresh and interesting to use. Find out more about Snapchat and how to use it here.

Viber

Viber

Free
Get from the App Store.

Viber isn't in quite the same league as Whatsapp, Facebook Messenger or Snapchat when it comes to global popularity, but in some countries, such as Australia, it's the messaging app of choice.

It's much like Whatsapp and Facebook Messenger in its capabilities, though, so it really depends on what your friends are using when it comes to choosing between the three. You'll get group chats, stickers to send and more.

Twitter

Twitter

Free
Get from the App Store.

Twitter is a surprisingly effective app for messaging. The public tweet service is not designed as a messaging app, but its Direct Messages (DM) lets you send texts, videos and pictures to individuals or groups that no other Twitter users will be able to see.

It's not the most practical messaging app and it might be a bit of a controversial inclusion, but Twitter has recently removed the character cap from DMs so it's much easier to use than it used to be and can come in handy if you don't have any other contact details for the person you want to message.

Skype

Skype

Free
Get from the App Store.

Skype is a versatile messaging app that was acquired by Microsoft in 2011. It's best known for its video calling capabilities, but it can also be used as a messaging app to send videos, texts and pictures just like the other apps mentioned in this round-up.

Kik

Kik

Free
Get from the App Store.

Kik seems to be relatively unknown among most circles, but for university students and other younger audiences it's a popular messaging service of choice. Kik is a messaging app that lets you chat with friends via the web, and doesn't require a phone number to set up. You simply choose a username, and then you can share pictures, videos, gifs, games and of course texts with friends.