Support for extensions to customize Chrome, the top-requested feature for Google's browser, has begun arriving for adventurous users.

Previously, extensions worked only for those who enabled the feature with a command line switch. Now the feature is enabled by default in the developer preview version of Chrome on Windows, Aaron Boodman, the Google engineer who oversees the extensions work, said in a blog post Wednesday.

"We're ready for a few more people to start using extensions--the kind ...