- This is about the website, not the Project Xanadu data format that is Tumbler, spelled with more actual vowels.
Tumblr is a social networking / blogging site that was owned by Yahoo!, then by Verizon, then by Automattic. It has a reputation for being very heavily into left-wing social-justice crusading and the angst of teens and twentysomethings. It also had a reputation of being full of porn, at least until late 2018 when the management abruptly decided to purge all of that. A rapid scramble by the Archive Team attempted to preserve some of the purged content.