Search the Invisible Web: 20 Free Resources

Unlike pages on the visible Web (that is, the Web that you can access from search engines and directories), information in the Invisible Web is just not visible to the software spiders and crawlers that create search engine indexes. Since this information makes up the vast majority of available content on the Web, we are potentially missing out on some pretty amazing resources.

However, that's where Invisible Web search engines, tools, and directories come in. There are many Invisible Web search tools that you can use to dive into this wealth of information, as you'll see from the following list. We'll take a look at twenty different search engines, directories, and databases you can use to uncover amazing content. 

The Internet Archive is an amazing database offering access to movies, live music, audio, and printed materials; plus, you can look at older, saved versions of nearly every site ever created on the Internet - over 55 billion at the time of this writing.

More archives

• Google News Archive Search
• Use the Web to Find Archives
• Five online archives that are worth a second look

USA.gov is an absolutely mammoth search engine/portal that gives the searcher direct access to a wide variety of information and databases from the United States government, state governments, and local governments. This includes access to the Library of Congress, an A-Z government agency index, the Smithsonian, and much, much more.

More government resources

• The Top Twenty Essential US Government Web Sites
• Free Public Records Search
• Google Uncle Sam

 The WWW Virtual Library gives you instant access to hundreds of different categories and databases on a wide variety of subjects, anything from Agriculture to Anthropology. More about this amazing resource: "The WWW Virtual Library (VL) is the oldest catalogue of the Web, started by Tim Berners-Lee, the creator of HTML and of the Web itself, in 1991 at CERN in Geneva. Unlike commercial catalogues, it is run by a loose confederation of volunteers, who compile pages of key links for particular areas in which they are expert; even though it isn't the biggest index of the Web, the VL pages are widely recognised as being amongst the highest-quality guides to particular sections of the Web."

Science.gov  searches over 60 databases and over 2200 selected websites from 15 federal agencies, offering 200 million pages of authoritative U.S. government science information including research and development results. More about this astonishingly useful resource: "Science.gov is a gateway to government science information and research results. Currently in its fifth generation, Science.gov provides a search of over 60 scientific databases and 200 million pages of science information with just one query, and is a gateway to over 2200 scientific Websites (see Science.gov fact sheet).

Science.gov is an interagency initiative of 19 U.S. government science organizations within 15 Federal Agencies. These agencies form the voluntary Science.gov Alliance which governs Science.gov."

Wolfram Alpha

 is a computational search engine, which means it stores a vast amount of pure data available to you via not only search, but also a question and answer format. More about Wolfram Alpha: "We aim to collect and curate all objective data; implement every known model, method, and algorithm; and make it possible to compute whatever can be computed about anything. Our goal is to build on the achievements of science and other systematizations of knowledge to provide a single source that can be relied on by everyone for definitive answers to factual queries."

 Alexa gives you specific analytical information about Web properties. More about this intriguing resource: "Alexa's traffic estimates are based on data from our global traffic panel, which is a sample of millions of Internet users using one of over 25,000 different browser extensions. In addition, we gather much of our traffic data from direct sources in the form of sites that have chosen to install the Alexa script on their site and certify their metrics."

Website owners especially can benefit from the data that Alexa offers; for example, here's a list of the top 500 sites on the Web. 

The Directory of Open Access Journals (DOAJ) indexes and provides access to quality open access, peer-reviewed journals. More about this online directory: "The Directory of Open Access Journals is a service that indexes high quality, peer reviewed Open Access research journals, periodicals and their articles' metadata. The Directory aims to be comprehensive and cover all open access scientific and scholarly journals that use an appropriate quality control system (see the section below) and is not limited to particular languages or subject areas. The Directory aims to increase the visibility and ease of use of open access scientific and scholarly journals—regardless of size and country of origin—thereby promoting their visibility, usage and impact."

More than 10,000 journals and millions of articles are searchable using the DOAJ. 

FindLaw is a gigantic repository of free legal information on the Internet, and offers one of the largest online lawyer directories available online. You can use FindLaw to locate an attorney, learn more about U.S. law and legal topics, and participate in the very active FindLaw community forums. 

 The Online Books Page, a service offered by the University of Pennsylvania, gives readers access to over two million books freely accessible (and readable) on the Internet. Users will also gain access to significant directories and archives of online texts,as well as special exhibits of particularly interesting classes of online books. 

The Louvre online simply begs to be discovered and cherished by art lovers all over the world. View thematic collections of art, get more information about the background of selected works, view art aligned with historical events, and much, much more. 

 One of the most vivid and interactive sites on this list of Invisible Web resources, the Library of Congress offers an incredibly rich and varied array of content. Collection highlights include Congressional records, digital preservation resources, the Veterans History project, and the World Digital Library. More about this national treasure: "The Library of Congress is the nation's oldest federal cultural institution and serves as the research arm of Congress. It is also the largest library in the world, with millions of books, recordings, photographs, maps and manuscripts in its collections."

If you're looking for data, then Census.gov is one of the first places you'll want to visit. More about this considerable resource: "The U.S. Census Bureau conducts demographic, economic, and geographic studies of other countries and strengthens statistical development around the world through technical assistance, training, and software products. For over 60 years, the Census Bureau has performed international analytical work and assisted in the collection, processing, analysis, dissemination, and use of statistics with counterpart governments in over 100 countries."

From geography to population statistics, you'll be able to find them here. 

Copyright.gov  is another U.S. government resource you can put in your Invisible Web search toolbox (for even more essential U.S. government sites, check out The Top Twenty U.S. Government Websites). Here, you can view works registered and documents recorded by the U.S. Copyright Office since January 1, 1978, as well as search records of registered books, music, art, and periodicals, and other works, including copyright ownership documents.

The  Catalog of U.S. Government Publications gives users instant access to electronic and print publications from the legislative, executive, and judicial branches of the U.S. government, with more than 500,000 records generated since July 1976. 

Bankrate, an online financial resource that's been around since 1996, offers a huge library of financial information; anything from current interest rates to articles on CUSIP and much, much more. 

 FreeLunch gives users the ability to quickly and easily find free economic, demographic, and financial data: "provides comprehensive and extensive historical and forecast data at the national and subnational/regional levels representing over 93% of global GDP. We cover more than 180 countries, over 150 global metro areas, all U.S. states, metro areas and counties. Our databases contain more than 200 million economic, financial, demographic and consumer credit time series, with 10 million added every year."

 PubMed, part of the National Center for Biotechnology Information, U.S. National Library of Medicine, is the perfect resource for anyone who's looking up medical or medical-related information. It offers more than 24 million citations for biomedical literature from MEDLINE, life science journals, and online books. 

 The FAA Data and Research pages offer information on how their research is done, the resulting data and statistics, and information on funding and grant data. Anything from Aviation Safety to Unruly Passengers (seriously) can be found here. 

 Learn more about how you can use the Invisible Web with the following resources:

What is the Invisible Web?: What is the Invisible Web, and how do you find it? Find out the basic definition of the Invisible Web and learn how to search its resources.

The Ultimate Guide to the Invisible Web: The Invisible Web is a mammoth resource that is mostly untapped. Learn how to discover Invisible Web resources with this comprehensive, ultimate guide to searching the Invisible Web's goldmine of information.

How Big is the Invisible Web?: The Hidden Web is the part of the Web that can't be easily accessed with a simple search engine query. How big is this part of the Web estimated to be?

What is the difference between the Invisible Web and the Dark Web?: The Dark Web and the Invisible Web are not the same thing, even though you might have heard them referenced as such in TV shows, movies, or books. Find out the important differences between these two very different terms.