How do you say you're welcome in Spanish?

Spanish for you're welcome: If as in a reply to 'thank you', "por nada" or "de nada". Saying "de (pronounced as day) nada" literally means "of nothing". It is like saying in English "think nothing of it" in response to someone's thank you.

If as in a greeting or salutation: "bienvenido/bienvenida" (sing) or "bienvenidos/bienvenidas (pl)

There are many ways to say you're welcome: "de nada", "por nada" or "a la orden".

De nada. Literally "it's nothing".

If you are using this to say something like "welcome to my house", then it would be "bienvenido a mi casa". "Bienvenido" is literally "well come".
De nada