One example is 'The Imitation Game'. It is based on the true story of Alan Turing. Turing was a brilliant mathematician who played a crucial role in cracking the Enigma code during World War II.
One way is to look for historical records. If there are documents, newspaper articles, or official reports that match the events in the story, it's likely based on a true story. For example, if a movie claims to be about a real - life crime, you can search for police records or court transcripts.