Custom Search Engines (CSEs) are powerful tools for searching over the pages of your site, as well as providing links to your favorite resources across the web. Because they provide great search functionality with the option to specify a subset of Google's web index, they're perfect for us to use in our Google Help Centers.

We've rolled out CSEs to many of our product Help Centers already, including the Custom Search Help Center, and we're also using it on our main Google Help page.

The Help Center search engines use several key features of CSEs such as refinements and labels to identify result sources, and Subscribed Links for certain help queries, like this one in the Analytics Help Center.

Because Help Center searches will now include content from product pages, developer documentation, Google blogs, and help groups, we hope that search will be an even more effective tool to help you find answers to your Google product questions. For example, failed searches - searches that don't return any results - decreased by 23% on the Analytics Help Center after we added a CSE.