That being said, the app that the players were chatting over was not entirely real — or, let us say, as real as advertised.
The building where 'The Circle' is shot (Source: YouTube)
Most features of the app were real. After all, even the show's creator, Tim Harcourt, agrees that the application is a glorified WhatsApp. (via Vulture)
The aspects, like its voice activation and recognition, were not exactly real.
Harcourt told Vulture that they initially did try to use the technology behind voice recognition, but it was not an easy task.
So, they have producers on standby to transcribe the voice commands and pass them onto the next room, or as Harcourt likes to call it, "there is some humanity in the app."
