The $300 Million Dollar Button: IxD, UX, or UI?


Trying to understand how one might describe the famous $300 Million button case study.

Here’s the article :

Basically, a site increased their revenue by changing the language from Register to Continue in an ecommerce
checkout flow.

Is this an example of Interaction Design?

Did it really increase revenue by $300M?

edit: article breaks it down. Wow. that must be some insane company like ebay or something