Open Directory Project


The Open Directory Project (ODP), also known as DMoz (for Directory.Mozilla, the domain name of ODP), is a multilingual open content directory of World Wide Web links owned by Time Warner that is constructed and maintained by a community of volunteer editors.


Project information

Motivation and founders

ODP was founded as Gnuhoo by Rich Skrenta and Bob Truel in 1998. At the time, Skrenta and Truel were working as engineers for Sun Microsystems. Chris Tolles, who worked at Sun Microsystems as the head of marketing for network security products, also signed on in 1998 as a co-founder of Gnuhoo along with co-founders Bryn Dole and Jeremy Wenokur. Skrenta was already well known for his role in developing TASS, an ancestor of TIN, the popular threaded Usenet newsreader for Unix systems. Coincidentally, the original category structure of the Gnuhoo directory was based loosely on the structure of Usenet newsgroups then in existence.

Gnuhoo to Newhoo to the Open Directory Project

The Gnuhoo directory went live on June 5, 1998, and was renamed Newhoo after a Slashdot article was posted in which posters claimed that Gnuhoo had nothing in common with the spirit of free software for which the GNU project was known and was simply a commercial enterprise seeking to construct an alternative to Yahoo! using volunteer labor.[1] ( Newhoo became ODP after it was acquired by Netscape Communications Corporation in October 1998 and the content was released under an open content license. Netscape was acquired by AOL shortly thereafter, and ODP was one of the assets included in the acquisition. AOL later merged with Time-Warner.

Directory growth and maturation

By the time Netscape assumed stewardship, the Open Directory Project had about 100,000 URLs indexed with contributions from about 4500 editors. On October 5, 1999, the number of URLs indexed by ODP reached one million. According to an unofficial estimate, the number of URLs in the Open Directory surpassed the number of URLs in the Yahoo! directory in April 2000 with about 1.6 million URLs. ODP achieved the milestone of indexing two million URLs on August 14, 2000, and the milestone of three million listings was reached on November 18, 2001. As of June 2004, ODP had about 4.4 million listings organized into over 590,000 categories derived from the contributions of some 63,000 editors. As of July 2003, the number of active editor accounts (that is, those editor logins which had not been removed, voluntarily resigned, or timed out due to inactivity of four months) was over 9,000.

Competing and spinoff projects

ODP has inspired the formation of two other major web directories edited by volunteers and sponsored by public companies: The now defunct Go directory (formerly owned by The Walt Disney Company), and Zeal (acquired by LookSmart). However, neither of these web directories have licensed their content for open content distribution, a strategy which ensured ODP's success in a highly competitive market. The concept of using a large-scale community of editors to compile online content has been successfully applied to other types of projects such as Wikipedia.

Three open content volunteer projects have been inspired by ODP's editing model: an open content restaurant directory known as ChefMoz (launched by ODP management), an open content music directory known as MusicMoz, and an encyclopedia known as Open Site. However, none of the three have yet achieved success at the level of ODP.

ODP content

Organization and scope of content

ODP uses a hierarchical ontology scheme for organizing site listings. Listings on a similar topic are grouped into categories, which can then include smaller categories.

Gnuhoo borrowed its initial ontology from Usenet. For example, the topic covered by the newsgroup was represented by the category Computers/AI/Artificial_Life. The original divisions were for Adult, Arts, Business, Computers, Games, Health, Home, News, Recreation, Reference, Regional, Science, Shopping, Society, and Sports. While these fifteen top-level categories have remained intact, the ontology of second- and lower-level categories has undergone a gradual evolution; significant changes are initiated by discussion among editors, and then implemented when consensus has been reached.

In July 1998, the directory became multilingual with the addition of the World top-level category. The remainder of the directory lists only English language sites. By May 2005, seventy-five languages were represented. The growth rate of the non-English components of the directory has been greater than the English component since 2002. While the English component of the directory held almost 75% of the sites in 2003, the World level grew to over 1,5 million sites as of May 2005, forming roughly one third of the directory. Ontology in non-English categories generally mirrors that of the English directory, although exceptions which reflect language differences are quite common.

Several of the top-level categories have unique characteristics. The Adult category is not present on the directory homepage, but it is fully available in the RDF dump that ODP provides. While the bulk of the directory is categorized primarily by topic, the Regional category is categorized primarily by region. This has led many to view ODP as two parallel directories: Regional and Topical.

On November 14, 2000, a special directory within the Open Directory was created for people under 18 years of age. Key factors distinguishing this "Kids and Teens" [2] ( area from the main directory are:

  • Stricter guidelines which limit the listing of sites to those which are targeted or appropriate for people under 18 years of age.[3] (
  • Category names as well as site descriptions use vocabulary which is age appropriate.
  • Age tags on each listing distinguish content appropriate for kids (age 12 and under), teens (13 to 15 years old) and mature teens (16 to 18 years old).
  • Kids and Teens content is available as a separate RDF dump.
  • Editing permissions are such that the community is parallel to that of the Open Directory.

By May 2005, this portion of the Open Directory included over 32,000 site listings.

Directory maintenance

Directory listings are maintained by editors on a daily basis. While some editors focus on the addition of new listings, others focus on maintaining the existing listings. This includes tasks such as the editing of individual listings to correcting spelling and/or grammatical errors, as well as monitoring the status of linked sites. Still others go through site submissions to remove spam and duplicate submissions.

Robozilla is a web crawler written to check the status of all sites listed in ODP. Periodically, Robozilla will flag sites which appear to have moved or disappeared, and editors follow up to check the sites and take action. This process is critical for the directory in striving to achieve one of its founding goals: to reduce the link rot in web directories. Shortly after each run the sites marked with errors are automatically moved to the unreviewed queue where editors may investigate them when time permits.

Due to the popularity of the Open Directory and its resulting impact on search engine rankings, domains with lapsed registration that are listed on ODP have attracted domain hijacking, an issue that has been addressed by regularly removing expired domains from the directory.

While corporate funding and staff for the ODP have diminished in recent years, volunteerism has resulted in the creation of new and improved editing tools, such as linkcheckers to supplement Robozilla, category crawlers, spellcheckers, search tools that directly sift a recent RDF dump, bookmarklets to help automate some editing functions, and tools to help work through unreviewed queues in multiple ways.

License and requirements

ODP data is made available for open content distribution under the terms of the Open Directory License, which requires a specific ODP attribution table on every Web page that uses the data. However the attribution requirement is often ignored by users of ODP data, and the enforceability of the terms of the ODP license has been challenged by some ODP data users. Such failure to adhere to the terms of the license generates a great deal of ill will among the community of volunteer ODP editors.

RDF dumps

ODP data is made available through an RDF-like dump that is published on a dedicated download server [4] ( An archive of previous versions is also available [5] ( From August 2003, a new version was usually published weekly on Wednesday or Thursday. In the past there have been gaps in RDF dump generation, the latest gaps of more than one week being September 2002 to February 2003, July 2003 and February 2005 to April 2005. An ODP editor has catalogued a number of bugs that are/were encountered when implementing the ODP RDF dump, including UTF-8 encoding errors (fixed since August 2004) and a RDF format that does not comply with the final RDF specification because ODP RDF generation was implemented before the RDF specification was finalized [6] (

So while today the so-called RDF dump is valid XML, it is not strictly RDF, but an ODP-specific format. Software to process the ODP RDF dump needs to take account of this.

Character encoding

The character encoding used by the ODP site used to be ISO 8859-1 for English and a language-dependent character set for other languages. Since 2000 the RDF dumps have been encoded in UTF-8; in early 2004 the whole site, including the English-language categories, was converted to UTF-8 encoding.

Users of ODP content

ODP data powers the core directory services for many of the Web's largest search engines and portals, including Netscape Search, AOL Search, Google, Alexa and AltaVista.

Other uses are also made of ODP data. For example, in the spring of 2004 Overture announced a search service for third parties combining Yahoo! search results with ODP titles, descriptions and category metadata. The search engine Gigablast announced on 12 May 2005 its searchable copy of the Open Directory. The technology permits search of websites listed in specific categories, "in effect, instantly creating over 500,000 vertical search engines".[7] (

As of May 29, 2005 the ODP listed 341 English-language Web sites that use ODP data as well as 175 sites in other languages.[8] ( However these figures do not reflect the full picture of use, as those sites which use ODP data without following the terms of the ODP license are not listed.

Many replicas of the ODP are using outdated data. Some smaller sites stopped using RDF dumps as they grew increasingly large, choosing to query live data directly from the ODP website.

In a larger context, the use of all Web directories, including Yahoo!, ODP, and LookSmart, has declined significantly as search engines have gained popularity.

ODP policies and procedures

Becoming an editor

There are restrictions imposed on who can become an ODP editor. The primary gatekeeping mechanism is an editor application process, presided over by ODP's meta editors, wherein editor candidates are required to demonstrate their editing abilities and disclose any and all website affiliations that might pose a conflict of interest. Approximately 90% of these applications are rejected, but re-application is the norm.

Editing model

ODP's editing model is a hierarchical one. Upon becoming an editor, an individual will generally have editing permissions in only a small category. Once they have demonstrated basic editing skill in compliance with the Editing Guidelines, they are welcome to apply for additional editing privileges, in either a broader category, or in a category elsewhere in the directory. Mentorship relationships between editors are encouraged, and internal forums provide a vehicle for new editors to ask questions.

Over time, senior editors may be granted additional privileges which reflect their editing experience and leadership within the editing community. The most straightforward are editall privileges, which allow an editor to access all categories in the directory. Meta privileges additionally allow editors to perform tasks such as reviewing editor applications, setting category features, and handling external and internal abuse reports. Cateditall privileges are similar to editall, but only for a single directory category; similarly, catmod privileges are similar to meta, but only for a single directory category. Catmv privileges allow editors to make changes to directory ontology by moving or renaming categories. All of these privileges are granted by staff, usually after discussion with meta editors.

In August 2004, a new level of privileges called admin was introduced. Administrator status was granted to a number of long serving metas by staff. Administrators have the ability to grant editall+ privileges to other editors and to approve new directory-wide policies, authorities that had previously only been available to root (staff) editors. A full list of senior editors is publically available. [9] (

Editing guidelines

All ODP editors are expected to abide by ODP's Editing Guidelines.[10] ( These guidelines describe: what types of sites may be listed and which may not; how site listings should be titled and described in a loosely consistent manner; conventions for the naming and building of categories; conflict of interest limitations on the editing of sites which the editor may own or otherwise be affiliated with; and a code of conduct within the community. Editors who are found to have violated these guidelines may be contacted by staff or senior editors, have their editing permissions cut back, or, as a last resort, lose their editing privileges entirely. ODP Guidelines are periodically revised after discussion in editor forums.

Site submissions

One of the original motivations for forming Gnuhoo/Newhoo/ODP was the frustration that many people experienced in getting their sites listed on Yahoo!. However Yahoo! has since implemented a paid service for timely consideration of site submissions. That lead has been followed by many other directories. Some accept no free submission at all. By contrast the ODP has maintained its policy of free site submissions for all types of site - the only one of the major general directories to do so.

One result has been a gradual divergence between the ODP and other directories in the balance of content. The pay-for-inclusion model favours those able and willing to pay, so commercial sites tend to predominate in directories using it. (See for example the initial impact on Looksmart. [11] ( Whereas a directory manned by volunteers will reflect the aims and interests of those volunteers. The ODP lists a high proportion of informational and non-profit sites.

Another consequence of the free submission policy is that the ODP has enormous numbers of submissions. The ODP now has approximately two million unreviewed submissions, in large part due to spam and incorrectly submitted sites. So the average processing time for a site submission has grown longer with each passing year. However the time taken cannot be predicted, since the variation is so great: a submission might be processed within hours or take several years.

Controversy and criticism

Allegations of abusive editing practices

There have long been allegations that volunteer ODP editors give favorable treatment to their own websites while concomitantly thwarting the good faith efforts of their competition. Such allegations are fielded by ODP's staff and meta editors, who have the authority to take disciplinary action against volunteer editors who are suspected of engaging in abusive editing practices. In 2003, ODP introduced a new Public Abuse Report System that allows members of the general public to report and track allegations of abusive editor conduct using an online form. [12] (

In a federal lawsuit in the United States, a prominent tax law firm known as J.K. Harris obtained a temporary restraining order and then a preliminary injunction against a volunteer ODP editor. The plaintiff alleged, in part, that the editor in question had engaged in abusive editing practices that violated both state and federal laws restricting unfair competition. The Honorable Claudia Wilken, United States District Judge for the Northern District of California, found that this allegation did not justify injunctive relief, but granted injunctive relief on other grounds.[13] (

Early in the history of the ODP, its staff gave representatives of selected websites, such as Rolling Stone magazine, editing access at ODP in order to list many individual pages on those websites. This led to allegations of unfair competition and unethical quid pro quo. Some volunteer editors perceived this to be a sellout of the "grass roots" principles on which ODP was based. The use of such professional content providers lapsed and the experiment has not been repeated.

Ownership and management of ODP

Underlying much of the controversy surrounding ODP is its ownership and management. Many of the original GnuHoo volunteers felt that they had been deceived into joining a commercial enterprise, but most of the initial controversy died down when the project was renamed NewHoo. Moreover, when Netscape acquired the project, renamed it ODP, and released ODP's content under an open content license, criticism of the ODP all but disappeared. However, as the community of editors at ODP began to grow, and ODP's content became widely used by most major search engines and web directories, the issue of ODP's ownership and management resurfaced.

At ODP's inception, there was little thought given to the idea of how ODP should be managed, and there were no official forums, guidelines, or FAQs. In essence, ODP began as a free for all. Even after ODP set up its internal editor forums, many editors remained blissfully unaware that these forums existed until they were directed to the forums by one of their fellow editors. Moreover, given that ODP had no official guidelines at first, ODP editors simply hashed out some sort of consensus among themselves and published unofficial FAQs.

As time went on, the ODP Editor Forums became the de facto ODP parliament, and when one of ODP's staff members would post an opinion in the forums, it would be deferred to as an official ruling. (In other words, "Staff has spoken.") There was also a short-lived attempt at moderation of the ODP Editor Forums, but it was abandoned as being the antithesis of the egalitarian principles on which the ODP community was supposed to be based. Even so, ODP staff began to give trusted senior editors additional editing privileges, including the ability to approve new editor applications, which eventually led to a stratified hierarchy of duties and privileges among ODP editors, with ODP's paid staff having the final say regarding ODP's policies and procedures.

Allegations that ODP editors are removed for criticizing ODP's policies

ODP's paid staff has imposed controversial policies from time to time, and volunteer editors who openly dissent often find their editing privileges removed, an ongoing situation which has been chronicled at the XODP Yahoo! eGroup since May of 2000. The first noteworthy expose was Life After the Open Directory Project, a June 1, 2000 guest column written for by David F. Prenatt, Jr. (former ODP editor 'netesq'), who founded the XODP Yahoo! eGroup after losing his ODP editing privileges.[14] ( Another noteworthy example was the volunteer editor known by the alias The Cunctator, who was banned from the ODP soon after submitting an article to Slashdot on October 24, 2000, which criticized changes in ODP's copyright policies.[15] (

Over time, discussion of ODP's purported shortcomings on the XODP Yahoo! eGroup has diminished to a fraction of its initial frequency. (I.e., from 891 postings in 2001, to 312 postings in 2002, to 327 postings in 2003, to 18 postings as of September in 2004.) Critics of XODP assert that this is proof of XODP's declining relevancy. However, critics of ODP claim that this diminished level of discussion is proof of XODP's efficacy in providing a more or less comprehensive overview of ODP's shortcomings. Meanwhile, uninhibited discussion of ODP's purported shortcomings has become more commonplace on more mainstream Webmaster discussion forums, such as WebMasterWorld and SitePoint.

Editor removal procedures

ODP's editor removal procedures, which are overseen by ODP's staff and meta editors, are frequently criticised. According to ODP's official editorial guidelines, editors are removed for abusive editing practices or uncivil behaviour. However, discussions that may result in disciplinary action against volunteer editors take place in a private forum which can only be accessed by ODP's staff and meta editors, and volunteer editors who are at risk of losing their editing privileges may not be given any notice that such proceedings are taking place, much less notice of an adverse decision. The rationale that is publicly asserted for this policy is that volunteer editors are assumed to know when they are violating ODP guidelines.

In the article Editor Removal Explained, ODP Meta Editor Arlarson states that "a great deal of confusion about the removal of editors from ODP results from false or misleading statements by former editors". [16] (

ODP has a standing policy that prohibits any current ODP editors in a position to know anything from discussing the reasons for specific editor removals. In the past, this has led to claims that many ODP editors are left to wonder why they cannot login at ODP to perform their editing work. However, ODP is now set up in such a way that when someone attempts to login at ODP using a deactivated editor login, a generic web page is displayed that informs a removed editor that a final decision has been made regarding the deactivation of his or her login and providing a list of possible reasons as to why such a decision might have been made. At the same time, a software glitch can result in the same page being displayed when an editor login has simply timed out and the editor in question is in fact eligible for reinstatement. Consequently, the ambiguity typically associated with editor removal procedures remains an ongoing issue.

Number of editors

As at December 13, 2003, the ODP front page stated 60,112 editors. However, this is not the number of editors currently contributing to the ODP, due to the fact that ODP tracks the total number of editor logins ever created rather than the number of currently active editors. Based on editor numbers gathered from the publicly available RDF dump, the ratio of total versus active editors is roughly 7 to 1. After an inactive period of four months, many of these logins time out. Other logins that are included in the overall tally represent the logins of former editors who have had their editing privileges removed. Moreover, according to ODP's critics, when ODP editor logins are intentionally deactivated, many former editors simply reapply under an assumed identity, leading to even greater exaggeration in the number of active ODP editors. ODP staff has occasionally promoted the ODP by mentioning the total number of editors without revealing that it is not the number of currently active editors.

Size of directory

As of December 8, 2003, the Open Directory Project homepage claimed that their directory contained 4,008,147 websites and 533,951 categories, but it was not entirely clear how much of this data was made available to non-editors and/or ODP licensees by virtue of the ODP RDF dump. In particular, it is not known whether the data at that time included site and category totals for ODP Editor Bookmarks and the hidden ODP "Test" categories that cannot be viewed by non-editors, neither of which are included in the RDF dump. The current front page totals do exclude these categories (and sites in them) however.

Allegations of blacklisting

Critics claim that sites are unjustly blacklisted whereas the response of the Open Directory Project is their editors are only employing a legitimate defense against linkspam.

Private editor forums

Critics of ODP have questioned the propriety of ODP having private editor forums in what is purportedly an open project, as both Go and Zeal have always allowed public access to their forum discussions. However, the defenders of ODP's private forums assert that such forums are necessary for the discussion of matters that are internal to ODP. Even so, some of these private forum discussions have been published outside of ODP after being forwarded to ODP's critics by anonymous ODP insiders. [17] (


The ODP Editor Forums were originally run on software that was based on the proprietary Ultimate Bulletin Board system. In June 2003, they switched to the PHPBB system. The ODPSearch software is a derivative version of ISearch and is open source, licensed under the Mozilla Public License.

The ODP database/editing software is closed source, although Richard Skrenta of ODP did say in June 1998 that he was considering licensing it under the GNU General Public License. This has led to criticism from the aforementioned GNU project and other proponents of free software, many of whom also criticise the ODP content license.

As such, there have been some efforts to provide alternatives to ODP (see below). These alternatives would allow communities of like-minded editors to set up and maintain their own open source/open content Web directories. However, no noteworthy open source/open content alternative to ODP has yet emerged.

See also: List of web directories


  1. CmdrTaco, The GnuHoo BooBoo, Slashdot (June 23, 1998).
  2. Open Directory Project: Kids and Teens Directory.
  3. Open Directory Project: Kids and Teens Directory Editing Guidelines.
  4. Open Directory Project: RDF dump.
  5. Open Directory Project: RDF Archive.
  6. R. Steven Rainwater, ODP/dmoz Data Dump ToDo List.
  7. Gigablast Launches 500,000 Vertical Search Engines (May 12, 2005).
  8. Open Directory Project: Sites Using ODP Data.
  9. Open Directory Project: ODP Senior Editors.
  10. Open Directory Project: Editing Guidelines.
  11. Dave Jansik, When Giant Directories Roamed the Earth, The Search Lounge (March 2, 2005).
  12. Open Directory Project: Public Abuse Report System.
  13. EFF: J.K. Harris v. Steven Kassel. Preliminary Injunction [PDF].
  14. David F. Prenatt, Jr., Life After the Open Directory Project, (June 1, 2000).
  15. CmdrTaco, Dmoz (aka AOL) Changing Guidelines In Sketchy Way, Slashdot (October 24, 2000).
  16. Arlarson, Editor Removal Explained, Open Directory Project Newsletter (September 2000).
  17. Dumb-oz, (Reproduction of a thread from the internal ODP Editor Forum).

External links

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