Google has announced the official release on Windows of Chrome 4, an updated version of the company's Web browser. It offers a handful of significant improvements, including support for extensions and bookmark synchronization. Due to Chrome's rolling development model, these features have been widely used by testers for quite some time. The official release means that the new functionality will be rolled out to regular end users through the stable channel. In addition to the major feature enhancements, Chrome 4 also brings a performance boost. Its score in the Dromeo DOM benchmarks is a 45 percent improvement over the previous version.