Big Daddy
Infrastructure rebuild of Google's crawling and indexing stack that changed how redirects, canonicalisation and URL handling were processed.
What changed
Big Daddy replaced the data-centre software behind crawling and indexing rather than changing ranking factors directly. It altered how Google handled 301/302 redirects, URL canonicalisation and duplicate content, and reduced crawl allocation to sites Google judged to have poor link profiles. Google engineers discussed the rollout publicly as it moved across data centres between December 2005 and March 2006; only month-level precision is documented.
Timing
Rollout began 1 December 2005. Google declared it complete on 1 March 2006, 90 days later. Rankings typically remain unstable for the whole rollout window, so measurements taken inside it are not a reliable read on the outcome.