Patent searching can be an expensive undertaking, and there’s no doubt that a skilled searcher can add value to the results you receive. But sometimes a quick search to locate a filed patent or get an overview of the patent landscape before embarking on a more detailed examination is just what you need. In most cases, the search is simple and doesn’t require the more advanced search features on offer from paid search services. It’s also nice to be able to do it quickly, conveniently and for free.

That being the case, we’ve ignored feature sets and listed below the most popular free patent search resources … based on Internet traffic.

I’ve explained some of the metrics we’ve used below. Note that the numbers above change on a daily basis, so it might be different when you check for yourself.

The top result highlights some of the limitations of the available data. The statistics for the Google patent search service are actually for the overall Google search engine! So while the Google patent search service does offer some unique features for free, it’s not as popular as the above table makes out. And it’s not possible with public data to really compare the Google service with others due to the popularity of its general search engine confusing the results.

Therefore, the most popular free patent search website is FreePatentsOnline, which has also recently added a free chemical search service. At 1.6 million unique users per month it’s well ahead of the pack.

But sheer traffic popularity alone shouldn’t be the sole metric by which you measure the popularity of a website. For a service based website, it’s sometimes more interesting to compare visits per person over the month, which speaks more about the service and type of person accessing the site than raw traffic numbers alone. For FreePatentsOnline, there are at most 160k users which return to the site more than once a month, a small fraction of its overall traffic. For sites like PatentLens, all of its users return more than once a month, but it’s still a drop in the ocean compared to FreePatentsOnline overall returning traffic. Patents.com has 12 times the traffic of PatentLens, but only twice the number of returning users.

It’s difficult to draw any conclusions from that information, particularly given that these services are freely available for anyone to use. Perhaps the number is more a comment on the consequences of being prominent in Google. Often being listed high in Google’s search results for generic terms like “patents” will generate significant traffic, but not necessarily traffic that is highly targeted to your particular service. While other, more targeted links might send only a small trickle of users, but all of them are high users of the service.

Of the government sites, the US sites receives the most attention by far. Even though it’s scope is narrow, it beats some of the more general free search sites. Next is the European Patent Office. Looking at the government sites shows the imprecise nature of the data – there is some significant differences between the Alexa traffic ranking and the Compete.com unique users per month. There are a number of reasons for these differences, but sometimes it’s the result of advertising increasing the number of users hitting the site, but not actually using the service.

As mentioned above, the data for these sites is changing all the time, as are the services provided by those sites. It will be interesting to review these services again in 6 months time.

Please let us know if you have any favourites that should be added to the list.

Notes on the metrics used.

Three popular ways to compare website performance are Google PageRank, Alexa Traffic Rank and Compete.com. There are many others, but these three are free and commonly used.

Google PageRank is the method used by Google to rank websites on its search engine. The higher the PageRank (out of a possible score of 10), the more important Google thinks the website is. While the finer details of the method are known only inside Google (and for good reason), the basic algorithm uses the number of sites linking to a particular site as a measure of its popularity. The more sites that link, the more important it must be and the higher the PageRank. When ranking the relevance of search results, Google combines the PageRank value of a website together with the prominence of the particular search term on the page, which determines the order of results. You can check the PageRank of a website here.

Alexa Traffic Rank is a little different. Alexa ranks websites based on the overall traffic to that website. The lower the rank, the more traffic Alexa thinks your website receives. It’s almost an impossible task to determine the real traffic going to a website, but Alexa makes a reasonable estimate using the log files from many different ISPs and other service providers. One of the issues/features of using Alexa is that it measures traffic at the domain level, not the page. So, using Google as an example, Alexa doesn’t distinguish between http://www.google.com and http://www.google.com/patents

Compete.com is similar to Alexa Traffic Rank, but keeps data on subdomains, one of the key reasons for significant difference above.

And just so you can find them, here are the URLs:

# Name URL
1 Google Patent Search http://www.google.com/patents
2 Free Patents Online http://www.freepatentsonline.com
3 EAST (US Govt search) http://www.uspto.gov/web/offices/ac/ido/pssd/
4 European Patent Office (EPO) http://ep.espacenet.com/
5 Patents.com http://www.patents.com
6 IP Australia (AusPat) http://www.ipaustralia.gov.au/auspat/index.htm
7 Delphion simple search http://www.delphion.com/simple
8 Patent Lens http://www.patentlens.net/daisy/patentlens/patentlens.html
9 Surf-IP http://www.surfip.gov.sg/_patent-f.htm
10 Patent Analysis Search System http://www.patentanalysis.com/