Formal or causal?

Hi everyone,
I wanted to know what should I use when I'm talking with a Japanese person online.
I know if they were older than me I should use formal but what if they were as same as my age((! should I use formal because I don't know them or what(
Thank you so much!

Depends if it's business/formalities. If not, in my opinion stick to whatever you are comfortable with. As a foreigner, they don't expect you to follow all the rules anyways.

Due to my lack of "formal" experience in speaking japanese, I tend to get nervous and mix up casual/formal. For me, it makes the conversation float more naturally when sticking to "casual"(partially Kansai/Chugoku dialect).

Out of all the japanese people I've spoken to during my life, none have thought it awkward when I speak casual. Maybe a sign of amusement/entertainment, if anything :-P

Thank you so much!!

Don't expect to be taken seriously if you rely on the "I'm a foreigner so the rules don't apply to me" mindset.

Don't expect to be taken seriously if you rely on the "I'm a foreigner so the rules don't apply to me" mindset.

True, guess I explained myself wrong there. I meant they don't expect foreigners to follow the unwritten rules 100% without a fault.

Assuming it is on online messaging/hobby group online, or something like that, I would start with "polite" speech (what you are calling "formal" I assume) and see how they respond.

If it is any business related conversation, of course polite speech.

Thank you everyone for answering my question. I've understood.
I'll use polite.

I'm Japanese and it's common for us to keep on using keigo in written form but speak in casual form when we're meeting in person. Then we'd go home and write in keigo again.

The safest way is to pay attention to what form the other party is using. If they use casual form, you can switch to casual form. I sometimes switch between formal and casual depending on how they write on that specific thread of exchanges. For example, even if a friend was writing casual one day, if she writes formal on another day, I'd respond in formal.

Is it true? I thought you write causal to your friends.
Thank you!!!

Of course you can write casual to your friends, but people have the habit of using formal in written form as opposed to verbal form. Like I said, I go back and forth even when writing.