Obviously, it comes with a few conditions. It will not work with your neighbour's Wi-Fi network, but only on public and open networks. Secondly, it will not tell you the exact speed but just give you a rough idea, one that should be enough for you to decide on whether to connect to it or not. The third and most important bit of all, is that you will have to be running Android 8.1 Oreo on your smartphone.
To check the speed, you go to the same place on your smartphone, like you always do. Tap on Settings, then Wi-Fi. Tap on the Wi-Fi toggle to switch it on and you will now see not just the networks available, but also the speed provided by each of those public networks.
As for the categorisation, the speeds are classified into four labels, Very Fast, Fast, OK or Slow.
And now, for the most important bit on your path to free Wi-Fi...
Google on its support page indicates that network labelled as 'Very Fast' will let you "stream very high-quality videos". Indeed, this is the one that you will rarely see in India, unless you happen to be close to a Google Station, may be.
Public Wi-Fi can be spotty. For the first time, #AndroidOreo 8.1 lets you take out the guesswork & see the speed of networks before you hit connect. Rolling out now: https://t.co/lSzvCFgNk7 pic.twitter.com/60EmoPxUX4
— Android (@Android) January 22, 2018
'Fast' will basically let you "stream most videos", so it's basically good enough for streaming YouTube videos in standard definition.
The 'OK' label sits at the bottom end of this table. It means that you should be looking elsewhere if you want to stream videos. But if all you want to do is "read webpages, use social media and stream music" then it should be good enough for you to connect to.
Lastly, there is the 'Slow' label. As the name of the label rightfully implies, it is slow, but Google claims that these should still be good enough for Wi-Fi calling and sending messages (WhatsApp, Messenger and more). In short, you need to hunt for a better network.
Now only if we all were on Android 8.1 Oreo!