“Are you serious?” is a very common expression in English. It is similar to ask, “No kidding?”, “For real?” etc.
In spoken Chinese, this expression is also very common. As you’ve guessed out, there are various ways to express “Are you serious?” in Chinese. I’ll list a few frequently used Chinese expressions to say it in this post. Hope you can apply them to your real life conversations in Chinese. If you know any other ways to say it, please don’t be shy to share. :-)
nǐ shì shuō zhēn de?
你是说真的?
nǐ shuō de shì shíhuà?
你说的是实话?
nǐ dāngzhēn?
你当真?
zhēn de jiǎde?
真的假的?
nǐ méi kāiwánxiào?
你没开玩笑?
nǐ shì rènzhēn de?
你是认真的?