How do you measure the success of a UX design project?

Hard one. I'd probably look at all 4 of them. Just like you can't look at the success of a company by just looking at revenue, you should take into account multiple KPIs.

The success of a UX design project is measured by its impact on user satisfaction, engagement, and ultimately, business goals. Key metrics such as user feedback, retention rates, conversion rates, and usability testing results help gauge the effectiveness of the design in meeting user needs and driving desired outcomes. Additionally, observing how the design contributes to overall product adoption and brand perception can provide valuable insights into its success. Ultimately, a successful UX design project not only enhances the user experience but also positively impacts the bottom line of the business.

The success of a UX design project is best measured by its impact on user satisfaction and the achievement of predefined usability goals. Key metrics include user engagement levels, task completion rates, and feedback from usability testing sessions.