Usually, YW is a humble and friendly answer to thank you. In some cases, however, it depends on the condition.When you see yw in a text, it stands for you're welcome.It’s a casual way to reply when someone thanks you. For example, if a colleague says, Thanks for change my shift, you can respond with yw to admit their thanks and keep the conversation light. After knowing Yw mean these days people use it other platform such as instagram, facebook or more, so you can also use where you want.