Google announced a Google Stadia free offer to help people with dealing with the global pandemic. Effective immediately as of April 8, 2020, every Gmail user can go to the official website. When they sign in and start, they will get to use what is essentially a Stadia Pro trial for two months until June 2020. At that point, they can opt out of the subscription to avoid paying the $9.99 monthly fee.
This Google Stadia free Pro opportunity also applies to existing members. If someone has an active subscription, they will not be charged for it for the same two months every new user is getting for free.
Since this is giving free and paid members access to Pro, that means they also get to play all the Stadia Pro games for free during this two month period. At the moment, that includes titles like Destiny 2: The Collection, Grid, Serious Sam Collection, Spitlings, Stacks on Stacks (on Stacks), and Thumper.
However, while Google is making Stadia Pro free for two months for both new users and current subscribers, it is also adjusting the service slightly to account for increased usage. During this time, the default resolution will be 1080p instead of 4K. (You can change your settings in data usage.)
Once someone has made a Google Stadia account, it is theirs regardless of whether or not they maintain a Pro subscription. However, the Stadia Pro games work like PlayStation Plus and Games With Gold, where you can only play titles doled out as part of it while you are an active subscriber. Any Google Stadia games you purchase are yours forever.
Google Stadia is playable on computers, a TV with a Chromecast Ultra, and some Android devices in 14 countries. It also works on tablets or devices with Chrome browsers.