Adam McKay's The Big Short is based on a true story but features a few key inaccuracies. The critically acclaimed movie, which won the 2016 Academy Award for Best Adapted Screenplay, was based on the New York Times Bestselling book "The Big Short: Inside the Doomsday Machine" written by Michael Lewis. While the book is mostly considered an objective nonfiction account of the 2008 housing bubble and subsequent United States stock market crash, it places its focus on some but not all the main players that were involved in the real-life financial crisis.

https://screenrant.com/the-big-short-true-story-movie-changes/