Guess 4 is now Protocol 4
Guess 4, the classic number logic game, was renamed Protocol 4 with version 2.0 in April 2026. Same game at heart, same developer: crack a secret 4-digit code by logic. You can play the classic game right here.
What changed when Guess 4 became Protocol 4
- The same core: guess a 4-digit code and use the clues to close in on it.
- Real-time PvP duels: race another player to the same code, or set the code they have to break.
- A hacker world: ranks, contracts, a mining empire, syndicates and raids.
- Six languages and an iPad layout.
Protocol 4 shows its clues as correct positions and correct digits; the game above uses green and yellow dots, as in Number Guess. The bulls and cows guide explains both. See every release in the Protocol 4 version history.
Frequently asked questions
Is Protocol 4 the same game as Guess 4?
Yes. Guess 4 was renamed Protocol 4 with version 2.0 in April 2026, by the same developer. Players got the new name as a normal update.
Are the other apps called Guess4 made by the same developer?
No. Other developers have released games with that name since. The original Guess 4 by Hakan Özger continues as Protocol 4.
Is Protocol 4 free?
Yes, it is free on the App Store for iPhone and iPad, with optional in-app purchases.
Open Protocol 4 Open Number Guess