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
You cannot make your own chat filter because Roblox simply wont allow it. That being said, use the filter already provided to you by Roblox. I recommend you look up very basic scripting tutorials on youtube. Here is the link to their playlist. Hope this helps!
This is a custom chat and when ever I try to add roblox's filer, Nothing even happens :P