MOBG.io is a battle royale IO game that you can play for free with real players from all over the world. You are spawned with no weapons and it's up to you what you do next. You can find yourself a gun, or try hiding somewhere in the trees until an unaware enemy shows up. The game goes on until the last surviving player kills his final enemy.
The mechanic of the ever shrinking safe zone is also implemented in this game, so take care not to go outside the perimeter into the red area if you want to live.
Overall, Mobg.io is a pretty great game for anyone who's into online deathmatch and battle royale.