How & when do I bring this up to a boyfriend

I’m only 20 and I don’t date much older men so we’re still young and their views may change as they get older and I don’t want to waster their time if it’s a deal breaker. I don’t want kids. How and when would I tell them this? I personally think a few months in or whenever we’re getting serious or should I do it before we even date? It’s an uncomfortable topic to talk about on a first date and or when we’ve only been dating a few months I honestly would find awkward to talk about because who knows maybe they’ll think I’m crazy for talking about kids so fast but I also don’t want to waste their time if they want kids in the future.