You might wonder why they don’t just let everyone in. The developers use an invitation system for three main reasons: Server Stability:

Contrary to the name, 3wifi is not a new Wi-Fi protocol or a hardware brand. Instead, it is a operating in several major metropolitan areas—including parts of Shanghai, Bangkok, Istanbul, and Mexico City.

Happy surfing!

Invitation codes are the "access keys" to this closed community. Because they are often one-time use, they go fast: Check Megathreads:

That means is the golden age of the "hot" code. Within the next six months, the developers may patch this method and require phone number verification for every code, killing the anonymous "hot" market.

Have a working code? Share it in the comments below to help out the community (and to earn good networking karma).