do you put a comma before or after but

Whether to put a comma before or after "but" depends on the context and the function of "but" in the sentence.

In general, you do not need a comma before "but" when it is used as a coordinating conjunction to connect two independent clauses. For example: "I wanted to go to the store but it started raining."

However, you may need a comma before "but" when it is used as a contrasting conjunction to introduce a subordinate clause that contrasts with the main clause. For example: "I would have gone to the store, but it started raining."

In summary, the decision to use a comma before or after "but" depends on the specific grammatical context of the sentence.