今何をしてる vs 今何をしてるの


I think both are informal ways of saying "What are you doing (now)?"

What's the different between the る version and the るの version?




Firstly, it should be noted that ending a sentence with の like that is
_generally_ more feminine.

In more depth, の (when it is not a particle) can be viewed as a proxy for
another word. In a sentence like this, I think it's generally to safe to say
that it's something like 訳. Outside of that, in "何をしているの" the の tends to
soften the speaker's tone (hence why it is generally feminine). In this case,
the の is generally supplying a tone of seeking/giving explanation, which
you'll see written in beginner-level Japanese textbooks.

In a similar, more masculine sentence, 今、何してるんだ, the の (here, shortened to ん)
does not perform that softening role and is overshadowed by the だ which makes
the sentence more forceful. However, the "explanation" intonation is still
present.

