So I will give you a small script..
if payload.Value == "Badword" then
payload.Value = " [Not sent due to bad word]"
end
this is, when a Badword is said it will change a string immediately except how will I make it so when the are chatting, it will find that certain word in the sentence, it will take me for ever to come up with 1000 of those things O_o

2 comments
By the way Payload is a stringvalue
You need to use Roblox chat filter you cannot make your own chat filter. All user inputted text that is shown to others needs to be filtered.