San Francisco, Feb 23 (IANS): Twitter co-founder Evan Williams on Friday announced that he is stepping down from the board of directors of the the micro-blogging site at the end of the month, according to a filing with the US Securities and Exchange Commission.

"I'm very lucky to have served on the Twitter board for 12 years (ever since there was a board). It's been overwhelmingly interesting, educational, and, at times, challenging," Williams, who has served as the Chief Executive Officer (CEO) of Twitter, tweeted on Friday.

While expressing his appreciation for almost 4,000 Twitter employees "who are doing the hard work every day," "I will continue rooting for the team as I focus my time on other projects", he added, reports Xinhua.

Williams co-founded Twitter in 2006 with Biz Stone and Jack Dorsey and later succeeded Dorsey to essay the role of the company CEO in 2008 until 2010, when he was replaced by Dick Costolo.

He is currently the CEO of Medium, a San Francisco-based online publishing tech company that was launched by him in 2012.