"Fair use" gets invoked constantly, usually as a shorthand for "this should be fine." But it isn't a vibe check. It's a legal test with four factors, and courts weigh all four every time. This video walks through how that test actually works.

The four factors, at a glance

• 01Purpose and character of the use Is the use transformative — commentary, criticism, parody, education — or just a straight copy for the same purpose as the original?
• 02Nature of the copyrighted work Factual and published works get less protection than highly creative or unpublished ones.
• 03Amount and substantiality used How much was used, and whether it includes the "heart" of the original work.
• 04Effect on the market Does the use compete with or undercut the market for the original?