Google is discontinuing their their Google Site Search product, which is the paid version of using Google search technology to power your internal site search feature. They are telling customers to use the free custom search engine version instead, which is what we use on this site.
The product will be discontinued by the 4th quarter of this year. Google told us:
We are winding down the Google Site Search product over the next year, but will provide customer and technical support through the duration of license agreements. For GSS users whose contract expires between April 1st and June 30th, 2017, we are providing a free 3-month extension with additional query volume to allow more time for them to implement the necessary changes to their site. GSS customers may also take advantage of our Custom Search Engine solution, an ads-supported model that offers similar functionality. We continue to build out new functionality and invest in new technology that make enterprise search a great experience for our customers. Just recently, we introduced the general availability of Google Cloud Search for G Suite customers.
Many are asking why? Does Google think they can make more money of site search products by showing ads than charging per query? Or does Google just want to stop having a team support that product? It is unclear.
One WebmasterWorld member said "I suspect those Google Site Search publishers that ride it to the end will be greatly disappointed with Google Custom Search."
There are other paid alternatives as well.
Forum discussion at WebmasterWorld.