Question: Most of the time in all the Spanish speaking countries I've been in I've heard ***de nada*** as the reply to *gracias* or the equivalent of English *you're welcome* etc.

But after a while I became conscious that sometimes some people were instead saying ***por nada***.

Are they actually used in different grammatical situations? Does the *de* vs *por* depend on something in the topic of what the thanking was about?

Or is it purely up to how the speaker feels, or is one more prevalent in certain places? Or is one less formal or not condoned as official by the RAE?

Answer: 
In these Word Reference threads, *"[por nada](http://forum.wordreference.com/showthread.php?t=210100)"*, *"[por nada vs de nada](http://forum.wordreference.com/showthread.php?t=918235)"*, *"[No hay de que; de nada; por nada](http://forum.wordreference.com/showthread.php?t=309777)"*, almost everyone says it's the same expression and it depends on everyone's choice.

But in the second one, someone says *"por nada"* is regarded as *kind of rude* in Spain. I am not sure about this, but I can say that while studying Spanish (*note:* I learnt the one from Spain), I think I never heard *"por nada"* but just *"de nada"*.

And looking up the RAE for the word "[nada](http://buscon.rae.es/draeI/SrvltConsulta?TIPO_BUS=3&LEMA=nada)", you can see that only *"de nada"* is listed. So maybe, although this doesn't prove about it being rude, it shows it's apparently more spread in the other Spanish speaking countries in Central and South America than in Spain. Perhaps native speakers can confirm this.
*De nada* is usually used as a polite answer after *Gracias*. On the other side *Por nada* is used when you were working on something and you didn't have a result, so you were working for nothing. In my opinion, *Por nada* would be then impolite answer after *Gracias*!

Also, direct translate of the phrases would be:

> 
> De nada = You're welcome
> 
> 
> Por nada = For nothing.
> 
> 
>