An open standard is a standard that is publicly available and has various rights to use associated with it, and may also have various properties of how it was designed (e.g. open process).
The terms "open" and "standard" have a wide range of meanings associated with their usage. The term "open" is usually restricted to royalty-free technologies while the term "standard" is sometimes restricted to technologies approved by formalized committees that are open to participation by all interested parties and operate on a consensus basis.
The definitions of the term "open standard" used by academics, the European Union and some of its member governments or parliaments such as Denmark, France, and Spain preclude open standards requiring fees for use, as do the New Zealand and the Venezuelan governments. On the standard organisation side, the W3C ensures that its specifications can be implemented on a Royalty-Free (RF) basis.
Many definitions of the term "standard" permit patent holders to impose "reasonable and non-discriminatory" royalty fees and other licensing terms on implementers and/or users of the standard. For example, the rules for standards published by the major internationally recognized standards bodies such as the IETF, ISO, IEC, and ITU-T permit their standards to contain specifications whose implementation will require payment of patent licensing fees. Among these organizations, only the IETF and ITU-T explicitly refer to their standards as "open standards", while the others refer only to producing "standards". The IETF and ITU-T use definitions of "open standard" that allow "reasonable and non-discriminatory" patent licensing fee requirements.
The term "open standard" is sometimes coupled with "open source" with the idea that a standard is not truly open if it does not have a complete free/open source reference implementation available. 
Open standards which specify formats are sometimes referred to as open formats.
Many specifications that are sometimes referred to as standards are proprietary and only available under restrictive contract terms (if they can be obtained at all) from the organization that owns the copyright on the specification. As such these specifications are not considered to be fully Open.
The ITU-T is a standards development organization (SDO) that is one of the three sectors of the International Telecommunications Union (a specialized agency of the United Nations). The ITU-T has a Telecommunication Standardization Bureau director's Ad Hoc group on IPR that produced the following definition in March 2005, which the ITU-T as a whole has endorsed for its purposes since November 2005 :
The ITU-T, ITU-R, ISO, and IEC have harmonized on a common patent policy  under the banner of the WSC. However, the ITU-T definition should not necessarily be considered also applicable in ITU-R, ISO and IEC contexts, since the Common Patent Policy  does not make any reference to "open standards" but rather only to "standards".
In section 7 of its RFC 2026, the IETF classifies specifications that have been developed in a manner similar to that of the IETF itself as being "open standards", and lists the standards produced by ANSI, ISO, IEEE, and ITU-T as examples. As the IETF standardization processes and IPR policies have the characteristics listed above by ITU-T, the IETF standards fulfill the ITU-T definition of "open standards".
However, the IETF has not adopted a specific definition of "open standard"; both RFC 2026 and the IETF's mission statement (RFC 3935) talks about "open process", but RFC 2026 does not define "open standard" except for the purpose of defining what documents IETF standards can link to.
To reach interoperability in the context of pan-European eGovernment services, guidance needs to focus on open standards.
The word "open" is here meant in the sense of fulfilling the following requirements:
The Danish government has attempted to make a definition of open standards , which also is used in pan-European software development projects. It states:
- An open standard is accessible to everyone free of charge (i.e. there is no discrimination between users, and no payment or other considerations are required as a condition of use of the standard)
- An open standard of necessity remains accessible and free of charge (i.e. owners renounce their options, if indeed such exist, to limit access to the standard at a later date, for example, by committing themselves to openness during the remainder of a possible patent's life)
- An open standard is accessible free of charge and documented in all its details (i.e. all aspects of the standard are transparent and documented, and both access to and use of the documentation is free)
- By open standard is understood any communication, interconnection or interchange protocol, and any interoperable data format whose specifications are public and without any restriction in their access or implementation.
A Law passed by the Spanish Parliament  requires that all electronic services provided by the Spanish public administration must be based on open standards. It defines an open standard as royalty free, according to the following definition:
An open standard fulfills the following conditions:
- it is public, and its use is available on a free [gratis] basis, or at a cost that does not imply a difficulty for the user.
- its use is not subject to the payment of any intellectual [copyright] or industrial [patents and trademarks] property right.
The Venezuelan Government approved a "free software and open standards law". The decree includes the requirement that the Venezuelan public sector must use free software based on open standards, and includes a definition of open standard:
Article 2: for the purposes of this Decree, it shall be understood as
k) Open standards: technical specifications, published and controlled by an organization in charge of their development, that have been accepted by the industry, available to everybody for their implementation in free software or other [type of software], promoting competitivity, interoperability and flexibility.
The E-Government Interoperability Framework (e-GIF)  defines open standard as royalty free according to the following text:
While a universally agreed definition of "open standards" is unlikely to be resolved in the near future, the e-GIF accepts that a definition of “open standards” needs to recognise a continuum that ranges from closed to open, and encompasses varying degrees of "openness". To guide readers in this respect, the e-GIF endorses "open standards" that exhibit the following properties: • Be accessible to everyone free of charge: no discrimination between users, and no payment or other considerations should be required as a condition to use the standard. • Remain accessible to everyone free of charge: owners should renounce their options, if any, to limit access to the standard at a later date. • Be documented in all its details: all aspects of the standard should be transparent and documented, and both access to and use of the documentation should be free. The e-GIF performs the same function in e-government as the Road Code does on the highways. Driving would be excessively costly, inefficient, and ineffective if road rules had to be agreed each time one vehicle encountered another.
One of the most popular definitions of the term "open standard", as measured by Google ranking, is the one developed by Bruce Perens.  His definition lists a set of principles that he believes must be met by an open standard:
"Let's look at what an open standard means: 'open' refers to it being royalty-free, while 'standard' means a technology approved by formalised committees that are open to participation by all interested parties and operate on a consensus basis. An open standard is publicly available, and developed, approved and maintained via a collaborative and consensus driven process."
An "open standard" must not prohibit conforming implementations in open source software.
To comply with the Open Standards Requirement, an "open standard" must satisfy the following criteria. If an "open standard" does not meet these criteria, it will be discriminating against open source developers.
Ken Krechmer identifies ten "rights":
As an important provider of Web technology ICT Standards, notably XML, http, HTML, CSS and WAI, the World Wide Web Consortium (W3C) follows a process that promotes the development of high-quality standards .
Looking at the end result, the spec alone, up for adoption, is not enough. The participative/inclusive process leading to a particular design, and the supporting resources available with it should be accounted when we talk about Open Standards:
- transparency (due process is public, and all technical discussions, meeting minutes, are archived and referencable in decision making)
- relevance (new standardization is started upon due analysis of the market needs, including requirements phase, e.g. accessibility, multi-linguism)
- openness (anybody can participate, and everybody does: industry, individual, public, government bodies, academia, on a worldwide scale)
- impartiality and consensus (guaranteed fairness by the process and the neutral hosting of the W3C organization, with equal weight for each participant)
- availability (free access to the standard text, both during development and at final stage, translations, and clear IPR rules for implementation, allowing open source development in the case of Internet/Web technologies)
- maintenance (ongoing process for testing, errata, revision, permanent access)
The Digital Standards Organization (DIGISTAN) states that "an open standard must be aimed at creating unrestricted competition between vendors and unrestricted choice for users". Its brief definition of "open standard" (or "free and open standard") is "a published specification that is immune to vendor capture at all stages in its life-cycle". Its more complete definition as follows:
A key defining property is that an open standard is immune to vendor capture at all stages in its life-cycle. Immunity from vendor capture makes it possible to improve upon, trust, and extend an open standard over time."
- "The standard is adopted and will be maintained by a not-for-profit organization, and its ongoing development occurs on the basis of an open decision-making procedure available to all interested parties.
- The standard has been published and the standard specification document is available freely. It must be permissible to all to copy, distribute, and use it freely.
- The patents possibly present on (parts of) the standard are made irrevocably available on a royalty-free basis.
- There are no constraints on the re-use of the standard.
This definition is based on the EU's EIF v1 definition of "open standard", but with changes to address what it terms as "vendor capture". They believe that "Many groups and individuals have provided definitions for 'open standard' that reflect their economic interests in the standards process. We see that the fundamental conflict is between vendors who seek to capture markets and raise costs, and the market at large, which seeks freedom and lower costs... Vendors work hard to turn open standards into franchise standards. They work to change the statutory language so they can cloak franchise standards in the sheep's clothing of 'open standard'. A robust definition of "free and open standard" must thus take into account the direct economic conflict between vendors and the market at large."
See also: Open source hardware.
See also: Open format.
In 2002 and 2003 the controversy about using reasonable and non-discriminatory (RAND) licensing for the use of patented technology in web standards increased. Bruce Perens, important associations as FSF or FFII and others have argued that the use of patents restricts who can implement a standard to those able or willing to pay for the use of the patented technology. The requirement to pay some small amount per user, is often an insurmountable problem for free/open source software implementations which can be redistributed by anyone. Royalty free (RF) licensing is generally the only possible license for free/open source software implementations. Version 3 of the GNU General Public License includes a section that enjoins anyone who distributes a program released under the GPL from enforcing patents on subsequent users of the software or derivative works.
One result of this controversy was that many governments (including the Danish, French and Spanish governments singly and the EU collectively) specifically affirmed that "open standards" required royalty-free licenses. Some standards organizations, such as the W3C, modified their processes to essentially only permit royalty-free licensing. Oasis-Open allows committees to operate either on a RAND basis or a royalty-free basis, but OASIS does say to grant "open standards" when they are not royalty-free.
Patents for software, formulas and algorithms are currently enforceable in the US but not in the EU. The European Patent Convention Article 52 paragraph (2)(c) expressly prohibits algorithms, business methods and software from being covered by patents. The US has only allowed them since 1989 and there has been growing controversy in recent years as to either the benefit or feasibility.
A standards body and its associated processes cannot force a patent holder to give up its right to charge license fees, especially if the company concerned is not a member of the standards body and unconstrained by any rules that were set during the standards development process. In fact, this element discourages some standards bodies from adopting an "open" approach, fearing that they will lose out if their members are more constrained than non-members. Few bodies will carry out (or require their members to carry out) a full patent search. Ultimately, the only sanctions a standards body can apply on a non-member when patent licensing is demanded is to cancel the standard, try to rework around it, or work to invalidate the patent. Standards bodies such as W3C and OASIS require that the use of required patents be granted under a royalty-free license as a condition for joining the body or a particular working group, and this is generally considered enforceable.
Examples of patent claims brought against standards previously thought to be open include JPEG and the Rambus case over DDR SDRAM. The H.264 video codec is an example of a standards organization producing a standard that has known, non-royalty-free required patents.
[...] The tsunami that devastated South Eastern Asian countries and the north-eastern parts of Africa, is perhaps the most graphic, albeit unfortunate, demonstration of the need for global collaboration, and open ICT standards. The incalculable loss of life and damage to property was exacerbated by the fact that responding agencies and non-governmental groups were unable to share information vital to the rescue effort. Each was using different data and document formats. Relief was slowed, and coordination complicated. [...]
– Mosibudi Mangena, Opening address of SATNAC 2005