 | This is anexplanatory essay about theWikipedia:Verifiability policy. This page provides additional information about concepts in the page(s) it supplements. This page is not one ofWikipedia's policies or guidelines as it has not beenthoroughly vetted by the community. |
 | This page in a nutshell: Offline sources are just as valid as online sources. |
Wikipedia'sreliable sources guideline states that articles should be sourced with reliable, third-party, published sources.Even though Wikipedia is an online encyclopedia, there is no distinction between using online versus offline sources. While many editors use online sources, such as websites and online journals, many great sources are only available offline in printed books and paper journals. Don't let the fact that a printed book or journal is not available online scare you away from using them as asource in Wikipedia. Likewise, do not remove cited material merely because it is from an offline source.
That Wikipedia relies extensively on online sources is not surprising, considering the relative ease of accessing such materials. There is also an additional advantage of using online sources, because it allows all users to evaluate the source and its value to the article. However, this reliance on online sources can lead torecentism, where most articles and content are from theInternet era. It can also lead to an unfair bias against print books and print journals, where an editor's addition of material sourced from a book or print journal is reverted with the comment "Revert - I couldn't access and confirm this source online."
Books are a typical example of an offline source. These are often great resources for history, philosophy and literature, and they often contain information that can't be found online. Several ongoing projects, such asProject Gutenberg,Internet Archive,NLA Trove andGoogle Book Search, aim atdigitizing certain books or newspaper articles and presenting them online. Even if the books are online, it might be necessary to consult a print edition to double-check any errors from theOCR scanning.
Manyacademic journals only make shortabstracts available online. Other content providers, likeThe Wall Street Journal, publish their content behind apaywall that prevents non-subscribers from accessing the content. Other websites, like thePhiladelphia Inquirer, only publish their content online for a few weeks. Sometimes a source was once online, but now is offline (link rot).
Special care should be taken when using offline sources. Provision of full bibliographic information helps Wikipedia's readers and editors find the source when they need it, and also increases the source's credibility as areliable source. This is often done by using a fully-filled outcitation template such as{{cite book}} or{{cite news}}. Use of thequote= parameter within thosecitation templates provides some context for the reference. This is especially important when using the off-line source to support a fact that might be controversial or is likely to be challenged. Providing identifiers such as anISBN,OCLC number,Open Library number or similar can help others locate physical copies, as cataloguing data can often vary from one library to another.
Many offline sources are easier than you might think to find online. TheInternet Archive full text search, as well asInternet Archive Scholar, are often able to provide a copy or snippet from millions of academic papers, books and even TV programs.
Sometimes, the use of an offline source will be challenged. Be sure toassume good faith for the user who cited the offline source. They might even be able to provide you a scan or an excerpt from that source. Consider visiting your local library to obtain a copy. Even if the library doesn't have that particular book or journal article, it might be available throughinterlibrary loan. Also consider posting an inquiry on the relevantWikiProject, because some interested editors might have a copy of that source. The volunteers atWikiProject Resource Exchange might be able to help you coordinate your search.