WordPress co-founder and Automattic CEO Matt Mullenweg called the company’s Tumblr acquisition his biggest failure — but one he hasn’t given up on yet. The comments were made at the recent WordCamp Canada 2025 conference, where Mullenweg went live for a Town Hall session to connect with the open source-focused WordPress community. The exec noted that Tumblr was still on a different technical stack than WordPress — something he had intended to correct by migrating the back end to WordPress