How to Say "For Real" in Spanish

For “for real?” as a reaction, the everyday choice is ¿En serio? For “really/truly” as a statement, the most common general expression is de verdad.

The most common way

really, truly; used to say something is genuine or to confirm that you mean it

How to say it: Stress the last syllable: de ver-DAD. The d in verdad is soft, with the tongue between the teeth, not a hard English d.

neutral statement

seriously, in earnest; used when you want to be taken seriously or insist you are not joking
When to use it: Say it after a claim when you need someone to believe you are sincere.
surprised question
¿ ?
Really? For real? Used as a quick reaction to surprising or doubtful news
When to use it: Use it with friends, family, or colleagues when someone tells you something hard to believe.
emphatic

really, truly; a slightly more emphatic or literary variant of de verdad
When to use it: Use it when you want extra emphasis, especially in careful speech or writing.
fuller challenge
¿ ?
Are you serious? For real? A more explicit challenge to something surprising
When to use it: Use it when you want to stop and check that the other person is not exaggerating or joking.
casual slang
¿?
Really? For real? Very casual Mexican slang
When to use it: Use it only in informal speech in Mexico, among friends or people your own age.