In United States trademark law, the functionality doctrine prevents manufacturers from protecting specific features of a product by means of trademark law. There are two branches of the functionality doctrine: utilitarian functionality and aesthetic functionality. The rationale behind functionality doctrine is that product markets would not be truly competitive if newcomers could not make a product with a feature that consumers demand. Utilitarian functionality provides grounds to deny federal trademark protection to product features which do something useful. Patent law, not trademark, protects useful processes, machines, and material inventions. Patented designs are presumed to be functional until proven otherwise. Aesthetic functionality provides grounds to deny trademark protection to design features which are included to make the product more aesthetically appealing and commercially desirable. Aesthetic features are within the purview of copyright law, which provides protection to creative and original works of authorship.
Courts will look to the following factors when determining utilitarian functionality:
Whether a feature is essential to the use or purpose of the product; or
Whether a feature affects the cost or quality of the product; or
Whether granting of trademark for the exclusive use of the feature would put competitors at a significant non-reputation related disadvantage
As of 2014 the federal circuit courts are split on their utilitarian functionality analysis. Most circuits, such as the Fifth Circuit and the Sixth Circuit follow the Supreme Court's analysis in TrafFix Devices, which focuses on whether the feature is essential to the use or purpose of the product. The Federal Circuit in contrast focuses its analysis on whether permitting a product feature to be trademarked would impair competitors.