CiteULike is a web service which allows users to save and share citations to academic papers. Based on the principle of social bookmarking, the site works to promote and to develop the sharing of scientific references amongst researchers. In the same way that it is possible to catalog web pages (with Furl and delicious) or photographs (with Flickr), scientists can share citation information using CiteULike. Richard Cameron developed CiteULike in November 2004 and in 2006 Oversity Ltd. was established to develop and support CiteULike.
When browsing issues of research journals, small scripts stored in bookmarks (bookmarklets) allow one to import articles from repositories like PubMed, and CiteULike supports many more. Then the system attempts to determine the article metadata (title, authors, journal name, etc.) automatically. Users can organize their libraries with freely chosen tags and this produces a folksonomy of academic interests.
Initially, one adds a reference to CiteULike directly from within a web browser, without needing a separate program. For common online databases like PubMed, author names, title, and other details are imported automatically. One can manually add tags for grouping of references. The web site can be used to search public references by all users or only one's own references. References can later be exported via BibTeX or EndNote to be used on local computers.
Creation of entries and definition of keywords
CiteULike provides bookmarklets  to quickly add references from the web pages of the most common sites . These small scripts read the citation information from the web page and import into the CiteULike database for the currently logged in user.
Sites supported for semi-automatic import include Amazon.com, arXiv.org, JSTOR, PLoS, PubMed, SpringerLink, and ScienceDirect. It is also possible although more time consuming to add entries manually.
Entries can be tagged for easier retrieval and organisation. More frequent tags are displayed in a proportionally larger font. Tags can be clicked to call up articles containing this tag.
Sharing and exporting entries
New entries are added as public by default, which makes them accessible to everyone. Entries can be added as private and are then only available to the specific user. Users of CiteULike thus automatically share all their public entries with other users. The tags assigned to public entries contribute to the site-wide tag network. All public references can also be searched and filtered by tag.
In addition, the site provides groups that users can join themselves or by invitation. Groups are typically labs, institutions, professions, or research areas.
On line CiteULike entries can be downloaded to a local computer by means of export functions. A first export format is BibTeX, the referencing system used in TeX and LaTeX. The RIS file format is also available for commercial bibliography programs such as EndNote or Reference Manager. It also allows to import into the free Zotero bibliography extension of Firefox. Export is possible for individual entries or the entire library.
CiteULike gives access to personal or shared bibliographies directly from the web. It allows one to see what other people have posted publicly, which tags they have added, and how they have commented and rated a paper. It is also possible to browse the public libraries of people with similar interests to discover interesting papers. Groups allow individual users to collaborate with other users to build a library of references. The data are backed up daily from the central server.
CiteULike is written in Tcl, with user contributed plugins in Python, Perl, Ruby and Tcl; some additional modules are written in Java; data are stored using PostgreSQL There is no API but plugins can be contributed using Subversion. The software behind the service is closed source, but the dataset collected by the users is in the public domain.
About the site
The site stemmed from personal scientific requirements. The initial author found existing bibliography software cumbersome.
- Zlatić, V.; Ghoshal, G.; Caldarelli, G. (2009). "Hypergraph topological quantities for tagged social networks". Physical Review E. 80 (3 Pt 2): 036118. arXiv:0905.0976. Bibcode:2009PhRvE..80c6118Z. doi:10.1103/physreve.80.036118. PMID 19905191.
- Good, B. M.; Tennis, J. T.; Wilkinson, M. D. (2009). "Social tagging in the life sciences: Characterizing a new metadata resource for bioinformatics". BMC Bioinformatics. 10: 313. doi:10.1186/1471-2105-10-313. PMC 2760536. PMID 19781082.
- Hull, D.; Pettifer, S.; Kell, D. (Oct 2008). McEntyre, Johanna, ed. "Defrosting the digital library: bibliographic tools for the next generation web". PLOS Computational Biology. 4 (10): e1000204. Bibcode:2008PLSCB...4E0204H. doi:10.1371/journal.pcbi.1000204. ISSN 1553-734X. PMC 2568856. PMID 18974831.
- CiteULike. "Frequently Asked Questions: Who is behind CiteULike?" .
- "CiteULike: A Researcher's Social Bookmarking Service, " Ariadne: Issue 51
- Hammond, T., et al. "Social Bookmarking Tools (I) A General Review." D-Lib.