It seems that all the participants need to have in common is the same 10 out of 11 digits of their mobile phone numbers.
"Text door neighbor" is the new mobile phone game in which people send text messages to numbers which have the same phone number as theirs apart from the last one, which could be lower, or higher.
And #textdoorneighbour yields some interesting results on social media. Unsurprisingly, not everyone wants to receive text messages from a complete stranger.
While others appear to be quite happy about it.
And for some, it simply doesn't work…
— Ricky Butcher (@WhereIDraw) January 6, 2016
So, instead of meeting a potential friend and exchanging numbers to stay in touch, #textdoorneighbor allows people to bypass old-fashioned acquaintance-making, whilst finding new text pals… or enemies.