What is a phased website rollout versus a big-bang launch?

A big-bang launch replaces the entire existing website with the new version at a single point in time, while a phased rollout implements the new site in stages, bringing sections, templates, or functionality online incrementally over a defined period. The two strategies represent fundamentally different positions on the risk-speed spectrum.

In a big-bang launch, the legacy site is replaced completely on go-live day. All new functionality, design, content, and integrations become available simultaneously. The preparation period is intensive: content migration, integration testing, staff training, and quality assurance must be thorough because there is no parallel system to fall back on. The benefit is a clean, immediate transition with no period of managing two systems. A phased rollout sequences the launch by module, section, or business function. The old site and new site may run in parallel temporarily as components are migrated. Earlier phases generate feedback and surface issues that inform later phases, reducing the probability of a cascading failure. The tradeoff is a longer total timeline, higher operational complexity from maintaining two systems concurrently, and delayed realization of the full project's benefits. Hybrid approaches also exist: launching core pages in a single cutover while phasing in secondary sections, advanced features, or regional variations over subsequent weeks or months.