Is funner a word?
The standard comparative form of “fun” is more fun, not funner (e.g., “It’ll be much more fun with you there”). However, “funner” is sometimes used as the comparative in informal speech (e.g., “It’ll be much funner with you there”).
QuillBot’s free Grammar Checker will identify errors with comparative forms like “funner” instead of “more fun” in your writing.