I agree with Amy Roe about 'net-friend'. I did a search for this word, but the only site I could find was a Chinese one, so I suspect it's 'Chinglish'. If you used this term, it would be clear what you meant, but it isn't generally used by English speakers. The invented term 'netizen' ( a combination of 'net' and 'citizen') exists, but it's not in common use. I've never heard anyone say it. 'Online friend' makes sense, and you could use this phrase if you want. It's not especially common, though.

I am a English native speaker, and I have never heard the phrase 'net-friend- used so I don't think there is a word for that. We sometimes use the phrase 'penpal' to refer to someone who you exchange letters with, who is usually from another country.

I agree, I have never heard net-friend used. Online Friend is the most common term used in the United States, with "netizen" being used mostly in written English, like in a newspaper article. I most often see the term "netizen" when reading an article about something happening in China, and it resulted in a large number of Chinese "netizens" using Weibo to voice their opinions.

I am a English native speaker, and I have never heard the phrase 'net-friend- used so I don't think there is a word for that. We sometimes use the phrase 'penpal' to refer to someone who you exchange letters with, usually from another country.