If you want to give your Uber driver a few extra bucks to say thanks, you can finally do it directly from the Uber app in many major cities.

On Thursday, the new wave taxi service is rolling out in-app tipping to 100 cities and metropolitan areas in the US and Canada, including some of its biggest markets, like New York City, San Francisco, and Los Angeles.

You don't have to tip your driver. Uber says, "tipping is neither expected nor required."

Despite requests from drivers, Uber had held off on including tipping in its app for six years. But it changed course in June when Uber, added it as an option for riders in three market. The company plans to roll out tipping to all the US markets it operates in by July 31.

Here's how tipping in Uber works: