PLRs provide a snapshot of the patent situation of a specific technology, either in a particular geography or at a point in time. Multiple snapshots across different points in time can show the evolution of a certain technology.
Espacenet allows users to search through over 100 million documents using
three types – Smart, Advanced and Classification – of search. Espacenet is a
free of use tool, provided by the EPO, and is used to perform patent searches
for inventions and technical developments.
Google patents harnesses google’s algorithms to search 17 patent offices for
free. Google provides this as a free service.