Google has taken on Amazon's Alexa, Apple's Siri, and Microsoft's Cortana with its own voice assistant called Google Assistant.

Google unveiled Google Assistant at its Google I/O conference in May 2016, pitching the new voice assistant as an improvement of the experience in Google Now, as well as an expansion of Google's existing "OK Google" voice controls.

Let's dive into how it works, which devices it is available on, and when you'll be able to use it.

Google Assistant is Google's latest iteration of an assistant. It's considered an upgrade or an extension of Google Now -- designed to be personal -- as well as an expansion of Google's existing "OK Google" voice controls.

For anyone who has been using Android for some time, you'll know that Google's Google Now feature smartly pulls out relevant information for you. It knows where you work, and it knows your meeting locations and travel plans, the sports teams you like, and what interests you. This data is presented to you in cards and through reminders on your Android device.

The "OK Google" side covers voice commands, voice searching, and voice-activated device control, letting you do things like send messages, check appointments and so on on your Android device, just like Apple's Siri on an iPhone or iPad. Google Assistant fuses all this together with a new bot-centric AI experience, designed to give you conversational interactions that cover both these areas and more.

Here's how Google explained its new assistant:

"The assistant is conversational -- an ongoing two-way dialogue between you and Google that understands your world and helps you get things done. It makes it easy to buy movie tickets while on the go, to find that perfect restaurant for your family to grab a quick bite before the movie starts, and then help you navigate to the theater."

Google Assistant is now available on the Google Pixel smartphones and Google Home. A limited version can also be accessed now in the Google Allo app. It is also coming to Android Wear devices via Android Wear 2.0, and Google has confirmed it will be made available for Android TV (both televisions and set-top boxes) as well as cars, presumably through Android-powered infotainment systems or even Android Auto.

Although Google has said that Google Assistant is exclusive to the Pixel smartphones, it has also said Google Assistant is appearing on Pixel phones first, suggesting it will be coming to other devices in the future. And since the Allo app works across almost all Android devices, as well as the iPhone, you could say that nearly all smartphones have access to Google Assistant.

However, the full Google Assistant experience is deeply integrated into the Pixel devices, and it is very different to the iteration in Allo, which is limited by comparison -- as we discuss below. We expect Google to have Google Assistant on all Android, Android Wear, and Android Auto devices before too long.

The thing to remember about Google Assistant is that it is designed to be conversational. That means you can ask a question and then ask several follow-up questions, and Google Assistant will be able to keep track of the conversation, determine context, and audibly respond with the right information. Here's how Google Assistant works across the different Google devices.

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With Google Assistant baked deep into the new Pixel smartphones, it's no surprise to find that there's instant access from the home button. Where this home button would once give you Now on Tap with a long press, that's now replaced by Google Assistant.

Long press on the home button and you enter the Google Assistant interface. This looks a lot like OK Google and can be triggered with the same hot word, with listening bars picking up your voice and instantly transcribing what you say onto the screen. You are then delivered a spoken reply, with results returned on the screen too. You can speak or tap your selections and the conversation continues.

For example, you can ask what you should have for dinner, and Google Assistant will locate local places to eat and serve up suggestions, with cards for a selection of restaurants. Google has further demonstrated this example by then booking a table using OpenTable.

Google Assistant also takes over things like navigation. Say you want to navigate home -- as you would with OK Google -- that still works, but you can also ask to find coffee shops on the way, for example.

Things run much deeper, though. You can ask what your next flight is, when your trip is, and you can ask to watch a particular programme on Netflix, or you can ask to view dog photos from your collection. There's also a wide range of fun options, like games, with a full panel show game hidden behind the "I'm feeling lucky" command.

Our experience so far suggests that Google Assistant is going to be huge and as it stands, it's a long way ahead of Siri, Alexa or Cortana.

Google Home is a connected speaker that also works as a smarthome control center and an assistant for the whole family. You can use it to playback entertainment throughout your entire house, effortlessly manage every-day tasks, and ask Google what you want to know. Google Home is able to do much of these things thanks to Google Assistant, working in a similar way to Alexa on Amazon's Echo.

The idea behind Google Home, however, is to be more integrated into your home environment. The Google Assistant is access with the OK Google hot word, or by tapping on the top of the Home device. Smarthome support comes in the form of IFTTT, Nest, Hue, SmartThings, so you'll be able to speak commands, as well as Chromecast support, meaning you can just speak to watch Netflix on your TV, which is really clever.

Like Amazon's Alexa, you can ask almost anything -- weights, measures, check your schedule, book an Uber, and more. Where this would all be phone-centric in the past, Google Assistant makes it easier to do all of this stuff through Google Home, just by using your voice.

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A lot of the original Android Wear experience relied on voice control. With Android Wear 2.0, the whole platform is now better equipped to deal with alternative inputs, like the swipe keyboard, as well as voice. Google Assistant is now available to better service your commands and demands. It can hold contextual conversations to deliver the information you want, as well as take other actions.

For example, you'll be able to ask Google to find an restaurant and navigate you there. In addition to a microphone, you'll also be able to hear replies through the watch's speaker (if supported by hardware). Best of all, Google Assistant works in English and German, with more languages coming soon. The LG Watch Sport and LG Watch Style are the launch devices for Android Wear 2.0, and, unfortunately, the update won't be made available for every Android Wear smartwatch, especially the older ones like the original Moto 360.

The Google Assistant you get with Android Wear 2.0 is a lot like what you find in the Pixel phones and Google Home. On the LG Watch Style, you can call upon Google Assistant by holding down the exterior crown. Assistant will ask you how it can help. You can use it do a range of tasks -- such as a quick conversion for foreign exchange rates, or sending a message, or  tracking your run or to launch an app.

And, if you're watching TV via Chromecast, you can use your Android Wear 2.0 watch a remote of sorts. Assistant will let you control any compatible smart home device -- from Samsung Smart Things to Nest. What you can't do seems to be hit or miss. For instance, you can't call an Uber through Assistant on the watch like you can through Google Home. You also can't get Spotify to play a specific playlist.

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The full integration of Google Assistant is coming to Android TV-compatible televisions and set-top boxes.

Pending a forthcoming software update, it will enable the new Nvidia Shield TV to be controlled almost entirely by voice, and Samsung SmartThings support will add the ability to control smart devices around the house. It will effectively turn your Shield into a Google Home or Amazon Echo, albeit one that plays media through a TV rather than speaker and has the ability to bring up on-screen results.

We've seen it work with a Nest thermostat, coffee maker and lighting in an early demo, so it's an excellent addition when it comes. Nvidia chose to use the game controller as the mic, however, so you do need to leave it lying around within earshot. Nvidia told us that was necessary. Putting the mic in the Shield TV box meant that it would have to be proudly displayed instead. 

We will update this piece with more details when the new Nvidia Shield TV and other Android TV devices get Google Assistant.

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Allo is Google's new smart chat app.

The messenger has started its roll out on Android and iOS and is designed to give you plenty of options when it comes to chatting to your friends. Rather than just giving you a straight-down-the-line messaging app, Allo makes chat more fun and interactive. It's based on your phone number -- like WhatsApp -- and seems to be going after all the popular chat apps, with emoji, stickers, and more.

One of its hottest features in the app is Google Assistant. Google took the voice assistant, as well as bots like the ones found in Facebook Messenger, and rolled them all into one product. In Allo, you can to ask Google Assistant questions by either typing "@google" and then asking your question or by using your voice to dictate.

Google Assistant will serve up results for or responses to your questions in Allo. Again, this is all conversational, so you can ask follow-up questions and the clever bot remains contextually aware. You can ask anything you'd type in to Google Search or Maps, including asking it to find you a place to eat nearby or how many euros are in a number of pounds. You can interact with it by asking it to tell you something interesting, show you something funny, or show a video about something specific, and it all shows up within the chat you're in. You don't need to leave the app.

One of the cool features is the in-chat game. Type "@google let's play a game" and you'll get the option to play emoji based trivia games. The app also features an incognito mode so that you can make your conversations more private, and you can even set them to self-destruct within a specified amount of time.

The Google Pixel phones launched in the US in October 2016, with Google Assistant baked to the core.

Google Home with built-in, voice-activated Google Assistant launched in the US in November 2016, with no word on when the speaker might be coming to the UK or other regions.

Google's long-awaited Android Wear 2.0 update gives you Google Assistant. Unfortunately, Android 2.0 won't be available for every Android Wear smartwatch. Older devices like the original Moto 360 and the LG G Watch aren't compatible. You can see the list of confirmed watch models here.

Keep in mind LG has designed the LG Watch Sport and LG Watch Style in collaboration with Google -- and these are the launch devices for Android Wear 2.0. The LG Watch Sport and Style will be available from 10 February in the US and will be coming to other regions soon after.

While making an announcement at CES 2017 in January, Google confirmed Google Assistant is coming to Android TV-compatible televisions and set-top boxes. Your Sony Bravia TV will get an update allowing you access to Google Assistant on your TV, and Google said you can expect the update sometime in "the coming months".

However, Google has confirmed that the £190 new Nvidia Shield TV (pending a forthcoming software update) will be the first to give you the full hands-free Google Assistant experience. And, like Google Home, Nvidia's Shield Spot -- a Wi-Fi-connected microphone/speaker peripheral that can be placed anywhere and connect to your Shield Android TV over Wi-Fi -- will be one of the first devices to spread Google Assistant around your house (a little like the Amazon Echo Dot). Nvidia hasn't yet announced a launch date for Spot.

Google has confirmed that Google Assistant is also going to be available in cars. Currently, this appears to be through compatible Android-powered in-car infotainment systems, but the company made no specific mention of Android Auto, nor did it announce a rollout date.

You can now use Google Assistant in the Google Allo app.

Based on the code in a new alpha release of the Google app for Android, it looks like Google Assistant is coming to older phones. The app includes code for adding the AI-powered bot to any phone, according to Android Police. Some Nexus 6P users have been able to access the Google Assistant welcome screen up with a long press on the home button, but it's not happening consistently across all handsets. 

Still, with the onslaught of Amazon Alexa and Samsung's upcoming Bixby, it makes sense for Google to get Google Assistant on as many devices as possible -- and as soon as possible.