Quantopian
Boston crowd-sourced quant platform (2011–2020): free web backtesting for anyone, capital allocated to the best-performing user algorithms. In this spoke it is the publisher of all-that-glitters, which used the platform's timestamped code archive to compare 888 strategies' backtests with their real out-of-sample records — a dataset no outside researcher could have built. The platform closed in 2020; its open-source pieces (Zipline, pyfolio, alphalens) outlived it. Thin node; expand when a second source lands.