This technical report chronicles the divergent evolution of the WebKit and Blink engines following their 2013 split, focusing on their distinct design philosophies and architectural paths. While both engines transitioned to multi-process models and GPU-accelerated rendering, WebKit prioritized memory efficiency and platform-specific integration for Apple devices, whereas Blink pursued a radical garbage-collection redesign for its DOM. The text details major internal overhauls, such as WebKit’s incremental layout engine rewrite and its high-performance four-tier JavaScriptCore engine, contrasting these with Blink’s "LayoutNG" and V8 engine. It also addresses significant differences in security and privacy, noting WebKit’s implementation of site isolation and its adoption of hardware-based protections like Pointer Authentication. Ultimately, the sources describe a shift from early divergence toward a modern alignment on web standards, driven by collaborative testing and interoperability initiatives. This comprehensive overview highlights how WebKit maintains a competitive balance between raw performance and resource constraints in the current browser landscape.