I wanted a simple thing: a weekly feed of new patent filings matching a keyword, so I could watch what competitors in a given technology are up to. The official routes all said no. The USPTO Open Data Portal returned 401 without an API key. The bulk data endpoint answered 503 for days. PatentsView had just moved to key-only access with an approval queue.
Then I opened DevTools on Google Patents and found that the whole site runs on one undocumented XHR endpoint. No key, no login, worldwide coverage.
The endpoint
When you search on patents.google.com, the frontend calls:
https://patents.google.com/xhr/query?url=q%3D(solid%2Bstate%2Bbattery)%26sort%3Dnew
