Methods and systems for instant messaging using a browser to eliminate the requirement of installation of instant messaging software at the user end is described. When a source user sends an instant message to a target user, the source server (the server which the source user is logged in) searches the information of the target server (the server which the target user is currently logged in) with the help of an instant messaging status server, and sends the instant message to the target server according to the search result. The target server then relays the instant message to the target user. The target server may also send a reply message to the source server, which in turn transmits the reply message to the source user. Preferably, at least one of users uses a browser and not an instant messaging client software.