What does Islam says about "chatting"? Is chatting with the opposite sex haram or not?

The shaitan (evil) can deceive people anytime so we should be alert...

Is chatting on the web permissible, what are its harms?

A Muslim’s talking and communicating whether mutually or virtually with one of his/her Muslim brother or sister is a good deed. But this is valid for the same group of gender. A man’s talking with a woman necessitates some points which should be taken into consideration in some aspects

For example, it is certainly not true to gossip, to lie and to talk about love, passion and things which turn on the carnal feelings. It makes no difference whether she/he is married or not for such a subject, but the sin of a married person is much more.   

But if the conversation reminds us about sacred subjects, Allah, death, afterlife and religious life; of course it is not prohibited besides is a good deed. Your criterion should be this. If you act in accordance with such rules then we can say that you are not committing sins and you are able to protect yourself. Also we recommend you to act in accordance with your conscience. If you feel a pang of conscience, immediately give up it.

For the couple thinking of marrying going somewhere alone and talking to each other is permissible and even sunnah with the condition that there must be one of their relative with them. But relations such as flirt are not permissible even if one of their relative is with them. As our religion prohibits and forbids adultery, it also prohibits and blocks off the ways which lead people to adultery.

Similarly, chatting and having small talks with the person you met on the internet is not permissible. But if the aim is to convey and to endear Islam, this is out of matter. Otherwise talking on a different way which brings minds wrong thoughts and feelings is not permissible, since such things astray people to wrong results.
Also, the essence of a family should base on a sure ground to be able to start and constitute a strong family. Therefore, as Islam advices parts to an arranged marriage, it considers their seeing each other as an essence as well.

From this point of view we can say that, the parts, who met with each other just on the internet but don’t have any idea about each other and whose families don’t have any contact with each other before, may not hold such a marriage, since such a marriage can end up disappointedly. As far as we are concerned, you or any other people should not try a marriage with such a method.-questionsonislam.com