With the latest update of Android 8.1 Oreo smartphones with a green robot on board have learned to determine the speed of Wi-Fi before connecting to the network.
In Wi-Fi settings, four network speed labels are now displayed: "Very fast", "Fast", "OK" and "Slow". The state of Internet speed will be displayed only for public Wi-Fi access points.
The difference between "Very fast" and "Fast" is the ability to "watch very high quality online videos" and "watch almost any video online" respectively. In Google, note that most of the cafe has a "OK" speed, which is enough for watching social networks and streaming music.
Source: The Verge