CRO should start when a site has sufficient traffic to produce statistically valid test results, a functional user experience that does not actively prevent engagement, and clearly defined conversion goals. It should not start when the site lacks basic usability, has no analytics infrastructure, or attracts too few visitors to reach statistical significance within a reasonable test window.
Prerequisites matter. If visitors are not even viewing the elements planned for optimization because of severe UX problems, CRO efforts will not produce meaningful results. The foundation must be in place first: working analytics tracking, a baseline understanding of current conversion rates, and enough traffic to run tests that reach significance. CRO also requires alignment between the page experience and visitor expectations. If visitors arrive expecting one thing based on the ad or search result and find something different, CRO on page elements will not fix the upstream mismatch. The right starting point is ensuring the foundational experience is functional, analytics are accurate, and goals are defined, then using research and data to identify evidence-based opportunities for the first round of testing. Starting CRO without this foundation risks optimizing elements that do not matter while ignoring structural problems that do.