Sporcle
Sporcle is our category pick. Founded in 2007 by Matt Ramme, the site is essentially a wiki for trivia quizzes — anyone can create one, the community votes on quality, the algorithm surfaces the best ones. The catalog has grown to several million quizzes covering every conceivable topic: world capitals, Friends episodes, Premier League stadiums, the periodic table, every Pokémon by name. The editorial reasoning for the pick: Sporcle works in both registers we list. The casual-fun side (entertainment trivia) and the actually-rigorous side (geography quizzes used by some teachers and quiz-bowl coaches as practice material) coexist on the same platform. The free tier is generous enough to never hit a paywall in normal use. The quiz format is consistent — type your answer in the box, see how many you got, share the result. It's the canonical online quiz destination because it has been online for nearly two decades and the format hasn't needed to change.