(Pocket-lint) - Casting, Google Cast or Chromecast represents one of the greatest steps in recent consumer technology. The ability to fling content from a phone or mobile device to a big-screen TV and control it from the palm of your hand is simple, but great.

For us it's better than pressure-sensitive displays or auto-tuning headphones, better than wearables and smartwatches, better than connected heating. Why? Because it's simple done well and it's all about entertainment.

That's why the Chromecast is such a breakthrough device but also why it's so misunderstood: it has no dedicated remote, it offers no user interface, it just puts things on your TV effortlessly. It's the simplicity that people often don't get, because it does so much by doing so little and that sends people into a flap.

The Chromecast Ultra is an easy and logical upgrade over the standard Chromecast, adding the ability to cast in 4K Ultra HD with luscious HDR (high dynamic range) if you've got one of the latest and greatest TVs.

58mm diameter x 14mm; 47g weight

HDMI male out, Micro USB power in

Mains power required for 4K content

We won't dwell on design too much, because the Chromecast Ultra adopts the format of Chromecast 2 and 3: a disc featuring a Micro-USB power input, attached to a short cable with HDMI. The HDMI plugs into your TV, while power is derived from the mains.

The two parts are magnetic so that you can tuck the device out of sight behind your TV, discreetly. There's no need for space in your AV cupboard, you don't need it sitting within view of an IR remote or anything else. Chromecast Ultra is basically invisible.

Well, it is and it isn't. The Ultra needs power to operate and so you'll need to feed that USB connection via the mains, so you'll have an extra cable to think about. It is a 2m cable, though, so should reach a wall-mounted TV.

This is a slight change from previous Chromecasts that could be powered from a USB socket on the rear of your TV (if it delivered necessary power). Now, if you connect to those lower-powered sockets, the Ultra won't allow you to stream in Ultra HD/4K and it will give you an on-screen notification to tell you to connect to the supplied power pack. Basically you have to do as you're told or the Ultra won't be ultra.

Wi-Fi to 802.11ac

Wired Ethernet connection option

Supports Android (4.1+), iOS (8.0+), Mac OS X (10.9+), Windows (7+)

Setup is as easy as plugging in the HDMI to the rear of your TV (or your receiver or other device if it supports 4K passthrough) and connecting to the power. That is all you need to physically do for Chromecast Ultra to get running and the rest is handled through the app.

Naturally, you'll need to have a TV that supports 4K Ultra HD and HDR to be able to view such content. If you want to watch Dolby Vision content you'll also have to make sure your display supports that - but the list of compatible TVs is growing.

It's also important to check the settings on your TV to ensure the HDMI input you have selected has the Ultra HD settings turned on. This is normally in the settings menu of your TV and has lots of different names, like Ultra HD Colour, for example. Although Chromecast Ultra will work without changing this setting, you might find you're not actually watching 4K content unless you change the TV settings, or that there's some banding or discolouration - especially on older TVs.

With that all sorted, next it's time to connect the Chromecast Ultra to your network. There are two options for this. The first is through Wi-Fi, which can be setup through the app - now called Home - to scan for your devices and identify your Ultra and ensure you're connecting to the right device.

Of course, streaming 4K HDR content via Wi-Fi might not work for everyone depending on where your TV is in the house and where your router sits. If your Chromecast Ultra is in your underground den, you might prefer a wired option, which is new for this version of Chromecast.

On the power supply you'll find an Ethernet socket on the side of the wall plug, meaning you can connect it to a wired network via cable. This has to be done at the start of the setup process and the Ultra will then seamlessly connect to the network without you having to do anything.

We connected it to a Homeplug device and found no problems at all, so if you don't want to add another Wi-Fi device then Ultra gives you that option, which is a huge advantage in this new version.

Depending on your TV, there's also the option force 50Hz to suit the UK market. If you're using an older TV that doesn't support different standards across both 50Hz and 60Hz (the latter for the US market), you might find some judder on some content. This option in the Home app can potentially fix it.

3840 x 2160 (4K) maximum resolution

HDR support, including Dolby Vision

Surround sound support

Chromecast forms a bridge between your TV and the internet, where the source of your 4K lives on a server. Using Chromecast Ultra is exactly the same as other casting devices. On your phone, you open the service you want to watch - e.g., Netflix or YouTube - and hit the cast button usually in the top right-hand corner of the app. You then find the content you want to watch on your phone and hit play and it starts playing on your TV.

The phone is simply the controller and you'll get playback functions like pause or forward and rewind on your phone to control the cast content. You'll be able to use your phone to search for other content or read emails or share selfies on Instagram, because it's the Chromecast that's doing all the work.

The important thing to understand is that your phone isn't sending that data to your TV. All it does is command the Chromecast Ultra to collect that content from the online source. It then finds the best quality it can and streams it for you. So, for example, you can't watch Luke Cage in 4K on your smartphone, but when Chromecast collects it, that's what you'll get (as long as you have a subscription to the 4K service with Netflix).

Netflix is the best example of Chromecast Ultra working to its best abilities because once you've hit the cast button and connected to Ultra, the Netflix app then shows the quality available, Ultra HD or HDR, for example.

Other sources aren't so clear. On YouTube, for example, you can change the quality of the video playback on your phone, but you're basically trusting Chromecast Ultra to get the best quality that YouTube will supply.

Fire up Marco Polo on Netflix and you're getting the best, with crisp 4K resolution for loads of detail and dramatic contrast thanks to its HDR delivery on Netflix. While there's a range of Ultra HD programming, HDR is a little scarce, with only the very newest titles offering this latest format.

Playback starts with a low quality stream and ramps it up using a variable bitrate system, depending on the feed you're taking it from. The aim is to get content playing quickly with no buffering and you'll notice that it clicks into being really sharp and clear after a short moment. For us, it's typically about 10 seconds or so, but this will be governed by your home network among other things.

One of the obvious downsides is that the Chromecast Ultra always outputs a 2160p PCM signal, regardless of the stream it is receiving. You might be watching a blocky 640 x 480 stream, but it will still be telling the TV that it's 2160p. There's no consistent way of getting the information of what you're actually watching, unlike native TV apps, which are normally supported by an info button on your TV's remote.

The one exception is HDR. When you start playing an HDR source, most HDR TVs will give you a notification that you're watching an HDR source and switch the display settings accordingly. For Netflix, the switch to HDR is instant, for YouTube the video needs to get going before the HDR stream arrives. This is then confirmed by the TV, but also shown if you hit pause, when the video title and quality will be shown (4K HDR, for example).

Although YouTube is often seen as a deposit for homemade videos, some of the HDR content available is stunning, although it's only been officially supported since late 2016. When you do stumble on a YouTube HDR video in 4K, the results are incredible. But be warned: there are a lot of videos titled as HDR that aren't in HDR, just straight 4K.

Chromecast also supports surround sound, but you're dependent on the source again and what comes with the stream and for your TV or sound system to then do the decoding.

There are a range of 4K sources available on Chromecast Ultra, but the two mentioned - Netflix and YouTube - are the biggest players in 4K Ultra HD at the moment.

Google Play will also offer Ultra HD content (although we still haven't really seen huge movements in content in the UK at least), but again makes for seamless casting with Chromecast Ultra.

The other major source of content is Amazon Video. When the Ultra first launched in 2016 Amazon didn't support Google Cast, but now it does - meaning you can also fling that content to your TV via Google's device.

Services like All4, BBC iPlayer and Now TV all support Chromecast Ultra, albeit not at this "ultra" higher quality - so the experience is no different to the existing devices, except it's perhaps a touch faster than before (again, we think a lot is defined by your network when casting). There's support in a lot of other apps too, like Vimeo.

Chromecast Ultra also supports audio, appearing as a supported device for Spotify, so you can easily send music to your TV (with album art) to play through your home cinema system. It's also supports Google Play Music, again allowing you play that content easily, as well as other music platforms.

Aside from those obvious media streaming applications, there's the point-to-point support that allows you send from a phone or browser to your TV. Apps like Google Photos support casting to your TV, so you can watch home movies or browse photos, swiping through your collection on your phone and having them appear on your phone, which is very cool.

Then there's mirroring for your Android device as well as casting from a Chrome browser. This will mirror directly on your TV so is a little more intensive on your network, but can be used to essentially get anything from your PC to your TV.

There's also wide support for Chromecast from embedded video in websites, so if you land on Zero Punctuation, for example, you can cast that video from within the website to watch it on your TV.

There's also support for Google Assistant, meaning you can you can talk to Google and get some responses to your questions on your TV and control content - although we've always found it to be easier just to use the phone for control.

So far this has been a tale of simplicity, great performance and flexibility. That's no different to existing Chromecast devices, but there's a small barrier to Chromecast Ultra: that you've bought a 4K Ultra HD TV which can already do most of this stuff.

Most recent Ultra HD TVs are smart TVs and many of them offer the big apps we've been talking about already. That means for something like Netflix, you probably already have access to 4K through your TV's existing app.

There's added complication and that's the DIAL casting protocol that Netflix also supports which allows you to control the TV app through your phone anyway. If you are signed into Netflix on your Smart TV, hitting the cast button will usually offer the TV as a casting destination and the experience is the same, but without the Chromecast. YouTube also offers a similar system, with the ability to control the Smart TV app through your phone, because it knows who you are from your Google account.

That renders Chromecast Ultra irrelevant for the majority of 4K watching that we do via Netflix, because the TV already offers the same service. And we suspect most people will be in the same position.

Of course, if you bought a 4K TV that's a little older or isn't "smart" (i.e., it's from lower down a manufacturer's range) then Chromecast Ultra is one of the cheapest and most convenient ways to unlock a full range of streaming content (Amazon being the main omission). There's also going to be a new lease of life for Chromecast Ultra with the launch of Google Stadia - Google's game streaming service - which will use Ultra as part of the package. If you've already got one, you'll just have to buy the Stadia controller and you'll be good to go.

There's one exception in this debate and that's about app updating. Smart TV manufacturers aren't hugely speedy to update apps, but smartphone apps often are - so using a dongle can mean you get access to newer services faster.

Verdict Chromecast Ultra is an easy and predictable upgrade for Google and a device that makes complete sense by supporting the latest formats for video streaming to your TV. However, unlike the previous two Chromecast devices that plugged a gap in your TV's skills, the Chromecast Ultra is likely to step on the toes of features that your TV already offers. And that, for many, will render it unnecessary. So, although we'd recommend the Chromecast Ultra without hesitation, we're yet to find anyone with a TV that can't already do the vast majority of the things this device offers. That sees it slide from a must-have device, to one that needs to rapidly increase its skill set and expand its offering to appeal to its target Ultra HD audience. That said, navigating content on your phone (be that iPhone or Android) is often much faster than your TV and the appeal of having the latest apps with wider support for Chromecast Ultra could tip the balance in its favour over your TV. Think carefully about Chromecast Ultra. It's a wonderful device, the greatest caster yet, making it perfect for the 1 per cent who might find use for it. For the other 99, however, chances are you simply won't need it in your life. First reviewed December 2016.

squirrel_widget_143466 Roku is s big name in streaming, offering access to all the major services in a slim device that supports the latest 4K HDR formats too. A simple remote makes it easy to control, while its biggest advantage is solid wireless connectivity. It's a great performer. Read the full Roku Streaming Stick+ review squirrel_widget_146520 Amazon is aggressive with its hardware, offering a 4K HDR capable streaming device at prices that are designed to sell - not to mention the benefit of regular discounts. The Fire TV Stick serves up Amazon's content as well as other popular services, with the benefit of Alexa integration and a remote. Read the Fire TV Stick 4K review

Writing by Chris Hall.