“My daughter has been acting strange the past few months,” wrote a parent on Yahoo Answers recently. “She’s always on this website called Tumbler. … Sometimes she says strange things like “my feels” ...

During its heyday from 2010 to 2015, Tumblr was its own vast universe made up of every fandom, aesthetic, and subculture imaginable. In the rearview, a singular Tumblr era has taken hold of the ...