The rules
Every rule a coin can carry. A creator fixes up to three at launch, the holders vote one more in every day. Each sentence below is exactly what the engine does, nothing more.
what a rule cannot do
No rule here stops a trade.
A real transfer hook can block a sell or tax a transfer. pump.fun creates the mint itself, so its coins cannot carry one. These rules work through the pay: break a rule and the fees of that shift go to the wallets that kept it. Someone who does not care about the pay can still sell whenever they like.