What is the difference between expanding foam and spray foam?

Difference between expanding foam and spray foam is mainly in terminology, application method, and scale. Expanding foam is general term for any foam that expands after dispensing from can or container, curing to fill gaps and voids. It includes both small canned foam like Great Stuff used for sealing cracks around windows and doors, often called expanding foam or canned foam, and larger two component spray foam used for insulation. Spray foam is type of expanding foam applied with spray gun and two component system that mixes at nozzle, expanding and curing quickly, used for insulating large areas like walls, attics, and roofs. So all spray foam is expanding foam, but not all expanding foam is spray foam. Canned expanding foam is one component, moisture cured, low pressure, used for small gaps, expands moderately, while spray foam insulation is two component, high pressure, expands more, provides higher R-value and air sealing. Spray foam is professional insulation product, expanding foam can refer to both DIY canned foam and professional spray foam.