You don't need to install most of the games onto your own console, although some can also be downloaded to your console to play direct.
Here then is everything you need to know about PlayStation Now.
How does it work?
PS Now is mainly a cloud-based service much like Netflix or Spotify, but for gaming. It hosts a wide collection of back catalogue and recent PS3 and PS4 titles (more than 700 games are available). You can access them at your leisure, all through a PS Now app on your PlayStation 4.
It uses technology acquired when Sony bought cloud gaming company Gakai and some of the technologies of the since-deceased OnLive. It allows you to play games that are not hosted on your own local console, but on massive servers elsewhere.
In a similar fashion to Xbox's Project xCloud and Google Stadia, the video of the game is streamed over the internet to the display you are using, with controller commands and your actions sent the other way. This happens almost instantly, so the effect is similar to running them from your console's storage.
Some PS4 games on the platform are available to download too, which work exactly like their equivalents bought from the digital PlayStation Store and are run from your console rather than remotely. You will need the hard drive space to install them and they only work while you continue to subscribe, but you will notice better graphical resolution and no lag or latency issues.
Do PS Now games look and play exactly like the games we can play on the PS4 directly?
Streamed video is in 720p rather than 1080p (or 4K). That doesn't matter so much for PS3 titles that were originally created in that resolution but a dip in detail and picture sharpness will be more noticeable for the PS4 line-up.
There are also reports of slight lag and latency issues when playing some of the faster, more demanding games. Latency is basically the time it takes between you pressing a button on the controller and seeing the results appear on screen. Because the controller response has to travel over the internet to a PlayStation Now server, be understood, then the video has to travel back over the internet to your console and TV, there is an unavoidable lag that wouldn't occur if you were playing the same game locally.
However, great strides have been made in ensuring the latency is as low as possible and you would be hard pressed to notice it on most games. The vast majority play just like they do on the console itself.
That includes the ability to play multiplayer on certain titles and PS Now games also reward gamers with Trophies like their disc-based counterparts.
Save games are stored in the cloud too, so you can pick up from where you left off no matter what device you played on last.
What devices is it available on?
Sadly, while PS Now was originally available on a wide selection of devices, it is restricted to PS4, PS4 Pro and Windows PCs these days.
And Windows PC owners can only stream games, not download them.
As far as we are aware, there are no plans to expand to other devices any time soon.
What internet speed do I need for PS Now?
It is recommended that you have a broadband connection of at least 5Mbps. Sony also suggests that you will get a more stable experience if you use a wired connection over a wireless one.
What games are available on PS Now?
At present, more than 700 games are available on the platform, which are made up of many PS3 titles and triple-A PlayStation 4 games, including God of War, Grand Theft Auto 5, Infamous Second Son, and Uncharted 4: A thief's End..
How much does PlayStation Now cost?
All games are available on a Netflix-style monthly subscription model.
First time users get a 7-day free trial period and it then costs £8.99 per month in the UK, $9.99 in the US.
You can also purchase a quarterly or yearly subscription up front, to get a discount. They are priced at £22.99 / $24.99 and £49.99 / $59.99 respectively.
When and how can I get it?
PS Now is available in the UK, US, Canada, Austria, Belgium, France, Germany, Ireland, Japan, Luxembourg, Switzerland and The Netherlands. You can get it through the PlayStation Store on your PS4.
The Windows PC version is available here.
What are the alternatives to PS Now?
Xbox currently runs a public preview version of its own cloud gaming platform, Project xCloud. You can find out more about it here: Project xCloud: Release date, beta and all you need to know about Xbox cloud gaming.
Google also has its own cloud gaming service, Stadia. But unlike PS Now, you don't get access to a whole library of games for one monthly fee. Instead, you have to pay for each game individually. You can learn more about it here: Google Stadia pricing, availability, games list, compatible devices and how it works.