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Copyright © 2014 W3C® (MIT, ERCIM, Keio, Beihang), All Rights Reserved. W3C liability, trademark and document use rules apply.
This document provides guidance on evaluating how well websites conform to the Web Content Accessibility Guidelines (WCAG) 2.0. It describes a procedure to evaluate websites and includes considerations to guide evaluators and to promote good practice. It does not provide instructions for evaluating web content feature by feature, which is addressed by WCAG 2.0 success criteria. This document is one of a series of informative W3C/WAI resources about Evaluating Websites for Accessibility that complements the WCAG 2.0 Documents. It does not define additional WCAG 2.0 requirements nor does it replace or supersede it in any way.
The methodology described in this document is intended for people who are experienced in evaluating accessibility using WCAG 2.0 and its supporting resources. It provides guidance on good practice in defining the evaluation scope, exploring the target website, selecting representative samples from websites where it is not feasible to evaluate all content, auditing the selected samples, and recording the evaluation findings. It is primarily designed for evaluating existing websites, for example, to learn about them and to monitor their level of accessibility. It can also be useful during earlier development stages of websites. It applies to static and dynamically generated websites, mobile websites and applications, and other types of websites. It does not specify particular web technologies, evaluation tools, web browsers, assistive technologies, or other software to use for evaluation. It is suitable for use in different evaluation contexts, including self-assessment and third-party evaluation.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
This 30 January 2014 Working Draft of Website Accessibility Conformance Evaluation Methodology (WCAG-EM) 1.0 addresses the comments received on the previously published Working Draft of 26 February 2013. It is a complete draft that addresses all issues raised to date, though some sections highlighted in the document need further feedback and refinement. This document is intended to be the final draft before publication of the methodology as an informative W3C Working Group Note.
The WCAG 2.0 Evaluation Methodology Task Force (Eval TF) invites discussion and feedback on this document by developers, evaluators, researchers, and others with interest in web accessibility evaluation. The group is looking for feedback on the following aspects in particular though comments on other aspects are equally welcome:
Please send comments on this Working Draft of Website Accessibility Conformance Evaluation Methodology 1.0 by 28 February 2014 to public-wai-evaltf@w3.org (publicly visible mailing list archive).
Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document has been produced by the WCAG 2.0 Evaluation Methodology Task Force (Eval TF, a joint task force of the Web Content Accessibility Guidelines Working Group (WCAG WG) and Evaluation and Repair Tools Working Group (ERT WG), as part of the Web Accessibility Initiative (WAI) Technical Activity.
This document was produced by two groups operating under the 5 February 2004 W3C Patent Policy. The groups do not expect this document to become a W3C Recommendation. W3C maintains a public list of any patent disclosures for WCAG WG and public list of any patent disclosures for ERT WG made in connection with the deliverables of each group; these pages also include instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
Evaluating the extent to which a website conforms to the Web Content Accessibility Guidelines (WCAG) 2.0 is a process involving several steps. The activities carried out within these steps are influenced by many aspects such as the type of website (e.g. static, dynamic, responsive, mobile, etc.), its size, complexity, and the technologies used to create it (e.g. HTML, PDF, etc.), how much knowledge the evaluators have of how the website was or is being developed, and the main purpose for the evaluation (e.g. to issue an accessibility statement, to plan a redesign process, to perform research, etc.).
This methodology, describes the steps that are common to website conformance evaluation processes. It highlights considerations for evaluators to apply these steps in the context of a particular website. It does not replace the need for quality assurance measures that are implemented throughout the design, development, and maintenance of websites to ensure their accessibility conformance. Following this methodology will help evaluators apply good practice, avoid commonly made mistakes, and achieve more comparable results. It supports common approaches and understanding for evaluating the extent of conformance of websites to WCAG 2.0, though in the majority of use cases it does not directly result in conformance claims.
This methodology does not in any way add to or change the requirements defined by the normative WCAG 2.0 standard, nor does it provide instructions on feature-by-feature evaluation of web content. The methodolody can be used in conjunction with techniques for meeting WCAG 2.0 success criteria, such as the Techniques for WCAG 2.0 documented by W3C/WAI, but does not require this or any other specific set of techniques.
In many situations it is necessary to evaluate the accessibility of a website, for example before releasing, acquiring, or redesigning the website. Periodic evaluation is also useful for monitoring the accessibility performance of websites over time. This methodology is designed for anyone who wants to follow a common procedure for evaluating the conformance of websites to WCAG 2.0. This includes:
WCAG 2.0 defines conformance requirements for individual web pages (and in some cases, sets of web pages), but does not describe how to evaluate entire websites. It also defines how optional conformance claims can be made to cover individual web pages, a series of web pages such as a multi-page form, and multiple related web pages such as a website. This is applicable when all web pages that are in the scope of a conformance claim have each been evaluated or created in a process that ensures that they each satisfy all the conformance requirements.
WCAG 2.0 conformance claims cannot be made for entire websites based upon the evaluation of a selected sub-set of web pages and functionality alone, as it is always possible that there will be unidentified conformance errors on these websites. However, in the majority of uses of this methodology only a sample of web pages and functionality from a website is selected for evaluation. Thus in the majority of situations, using this methodology alone does not result into WCAG 2.0 conformance claims for the target websites. Guidance on making statements about the outcomes from using this methodology is provided in Step 5.c: Provide an Evaluation Statement (Optional).
The information below, related to web accessibility essentials, evaluation, and WCAG 2.0 is important for using this methodology:
The following documents introduce the essential components of web accessibility and explain how people with disabilities use the Web. They are critical for understanding the broader context of web accessibility evaluation:
These are particularly important resources that outline different approaches for evaluating websites for accessibility:
This is the internationally recognized standard explaining how to make web content more accessible to people with disabilities. The following resources are particularly important for accessibility evaluation of websites:
For the purposes of this document, the following terms and definitions apply:
When a web page is one of a series of web pages presenting a process (i.e., a sequence of steps that need to be completed in order to accomplish an activity), all web pages in the process conform at the specified level or better. (Conformance is not possible at a particular level if any page in the process does not conform at that level or better.)
Satisfying all the requirements of a given standard, guideline or specification
The content would not conform if that technology is turned off or is not supported
Content patterns that are filled in by authors or the authoring tool to produce web content for end users (e.g., document templates, content management templates, presentation themes). Often templates will pre-specify at least some authoring decisions.
A non-embedded resource obtained from a single URI using HTTP plus any other resources that are used in the rendering or intended to be rendered together with it by a user agent
This methodology is used for thorough evaluation of websites using WCAG 2.0. Before evaluating an entire website it is usually good to do a preliminary evaluation of different web pages from the target website to identify obvious accessibility barriers and develop an overall understanding of the accessibility performance of the website. Easy Checks - A First Review of Web Accessibility describes an approach for such preliminary evaluation that is complementary to this methodology.
Users of this methodology are assumed to be knowledgeable of WCAG 2.0, accessible web design, assistive technologies, and of how people with different disabilities use the Web. This includes understanding of relevant web technologies, accessibility barriers that people with disabilities experience, assistive technologies and approaches that people with disabilities use, and evaluation techniques, tools, and methods to identify potential barriers for people with disabilities. In particular, it is assumed that users of this methodology are deeply familiar with the resources listed in section Background Reading.
This methodology is independent of any particular web accessibility evaluation tool, web browser, and other software tool. Many checks are not automatable, however, web accessibility evaluation tools can significantly assist evaluators during the evaluation process and contribute to more effective evaluation. For example, some web accessibility evaluation tools can scan entire websites to help identify relevant pages for manual evaluation. Tools can also assist in manually evaluating the many checks that are not automatable. Selecting Web Accessibility Evaluation Tools provides further guidance beyond the scope of this document.
This methodology can be carried out by an individual evaluator with the skills described in the section Required Expertise. However, using the combined expertise of review teams provides broader coverage of the required skills and helps identify accessibility barriers more effectively. While not required for using this methodology, the use of review teams is recommended when performing an evaluation of a website. Using Combined Expertise to Evaluate Web Accessibility provides further guidance beyond the scope of this document.
Involving people with disabilities including people with aging-related impairments helps identify additional accessibility barriers that are not easily discovered by expert evaluation alone. While not required for using this methodology, it is recommended that evaluators involve real people with a wide range of abilities during the evaluation process. Involving Users in Web Accessibility Evaluation provides further guidance beyond the scope of this document.
This methodology is designed for evaluating full, self-enclosed websites. This includes websites of organizations, entities, persons, events, products, and services.
Specific examples of websites include:
A website can be part of a larger website, such as the online shop in the preceding examples. A website can also be a clearly separable version of the website such as the mobile or Dutch language versions of the website, as shown in the preceding examples. This methodology can be applied to any such determinable website, regardless whether or not it is part of a larger website. The exact definition of a target website to be evaluated is determined as part of Step 1.a.
When a target website is defined for evaluation, it is essential that all web pages, web page states, and functionality within the scope of this definition are considered for evaluation. Excluding such aspects of a website from the scope of evaluation would likely conflict with the WCAG 2.0 conformance requirements for full pages and complete processes, or otherwise distort the evaluation results.
The preceding diagram shows a university website comprised of distinct areas; "Information for Students", "Information for Lecturers", "Courseware Application", and "Library Application". The "Courseware Application" includes "Physics Courses", "Medical Courses", and "History Courses" that are aggregated into the application. The university website also has individual web pages such as legal notices, sitemap, and other web pages that are common to all areas.
In the preceding example, if the university website in its entirety is defined as the target for evaluation then all of the depicted areas are within the scope of the evaluation. This includes any aggregated and embedded content such as maps of the campus, forms for online payments, and discussion boards, including when such parts originate from third-party sources. If only a specific website area, such as the "Courseware Application", is defined as the target for evaluation then all the parts of this area are within the scope of the evaluation. In this case, the scope of evaluation would include all depicted courses, as well as the individual web pages that are common to all areas of the university. See also the definition for Common Web Pages.
This methodology is applicable to the broad variety of websites. The following considerations apply to particular types of websites:
This methodology is designed to be flexible to facilitate its applicability in different situations and contexts. The following considerations apply to particular situations and contexts for an evaluation:
Website evaluation, according to this methodology, may be re-run after a short period; for example, when issues are identified and repaired by the website owner or website developer, or periodically to monitor progress. In such cases, for the barriers that were identified, include at least:
This section defines the stages and activities of an evaluation procedure. The stages are not necessarily sequential. Also the exact sequence of the activities carried out during the evaluation stages depends on the type of website, the purpose of the evaluation, and the process used by the evaluator. Some of the activities overlap or may be carried out in parallel. The following diagram illustrates the iterations between the stages defined in this section:
The workflow diagram depicts each of the five steps defined in this section with an arrow to the next step and arrows back to all of the previous steps. This way evaluators can proceed from one step to the next and return to any preceding step in the process whenever the evaluation reveals a need to return to any one of the previous steps: 1. Define the evaluation scope; 2. Explore the target website; 3. Select a representative sample; 4. Audit the selected sample and 5. Report the findings.
Note: See also considerations for Particular Evaluation Contexts that may influence how an evaluation procedure is carried out.
Methodology Requirement 1: Define the evaluation scope according to Methodology Requirement 1.a, Methodology Requirement 1.b, and Methodology Requirement 1.c, and optionally Methodology Requirement 1.d and Methodology Requirement 1.e.
During this step the overall scope of the evaluation is defined. It is a fundamental step that affects the subsequent steps in the evaluation procedure. It is ideally carried out in consultation with the evaluation commissioner (who may or may not be the website owner) to ensure common expectations about the scope of the evaluation. Initial exploration of the target website during this step may be necessary to better know specifics of the website and the required evaluation. Detailed exploration of the website is carried out in Step 2: Explore the Target Website.
Methodology Requirement 1.a: Define the target website according to Scope of Applicability, so that for each web page it is unambiguous whether it is within the scope of evaluation or not.
During this step the target website (the web pages and states of web pages that are in scope of the evaluation) is defined. This scope of the website is defined according to the terms established in the section Scope of Applicability.
To avoid later mismatches of expectations between the evaluator, evaluation commissioner, and readers of the resulting evaluation report, it is important to define the target website in such a way that for each web page it is unambiguous whether it is within scope or not. Using formalizations including regular expressions and listings of web addresses (URIs) is recommended where possible.
It is also important to document any particular aspects of the target website to support its identification. This includes:
Methodology Requirement 1.b: Select a target WCAG 2.0 conformance level ("A", "AA", or "AAA") for the evaluation.
Part of initiating the evaluation process is to define the target WCAG 2.0 conformance level ("A", "AA", or "AAA") to evaluate for. WCAG 2.0 Level AA is the generally accepted and recommended target.
Note: It is often useful to evaluate beyond the conformance target of the website to get a more complete picture of its accessibility performance. For example, while a website might not fully meet a particular conformance level, it might meet individual requirements from a higher conformance level. Having this information can help plan future improvements more effectively.
Methodology Requirement 1.c: Define the web browser, assistive technologies and other user agents for which features provided on the website are to be accessibility supported.
Particularly for new web technologies it is usually not possible that every accessibility feature, such as a 'show captions' function in a media player, is supported by every possible combination of web browser, assistive technology, and other user agents. WCAG 2.0 does not pre-define which combinations of features and technologies must be supported as this depends on the particular context of the website, including its language, the web technologies that are used to create the content, and the user agents currently available. Understanding Accessibility Support provides more guidance.
During this step a list of web browsers, assistive technologies, and other user agents that support the accessibility features on the website is defined. For some websites in closed networks, such as an intranet website where the computers used to access it are known, this baseline may be limited to the web browsers and assistive technologies used within this closed network. However, in most cases this baseline is ideally as broad as possible to cover the majority of user agents used by people with disabilities.
Methodology Requirement 1.d: Define any initial evaluation methods to be used to help evaluate conformance to WCAG 2.0 Success Criteria (Optional).
Determining conformance to WCAG 2.0 Success Criteria can be typically done in several ways. W3C/WAI provides a set of publicly documented (non-normative) Techniques for WCAG 2.0 that help evaluate conformance to WCAG 2.0 Success Criteria. However, it is not necessary to use these particular techniques (see Understanding Techniques for WCAG Success Criteria). Some evaluators might use other methods (inline with the requirements for custom techniques) to evaluate conformance to WCAG 2.0.
During this step, particular evaluation methods, if any are to be used, are defined. This does not limit the evaluator from using other additional evaluation methods at a later point, for example to evaluate particular content that was not identified at this early stage of the evaluation process. However, it is good practice to specify the initial evaluation methods to be used during the evaluation, as it helps to ensure consistent expectation between the evaluator and the evaluation commissioner.
Methodology Requirement 1.e: Define any additional evaluation requirements agreed on between the evaluator and evaluation commissioner (Optional).
An evaluation commissioner may be interested in additional information beyond what is needed to evalaute the extent of conformance of the target website to WCAG 2.0. For example, an evaluation commissioner might be interested in:
Such additional evaluation requirements that are agreed on with the evaluator need to be clarified early on and documented. This also needs to be reflected in the resulting report, for example, to clarify how the selection of the sample was carried out.
Methodology Requirement 2: Explore the website to be evaluated according to Methodology Requirement 2.a, Methodology Requirement 2.b, Methodology Requirement 2.c, Methodology Requirement 2.d, and Methodology Requirement 2.e.
During this step the evaluator explores the target website to be evaluated, to develop an initial understanding of the website and its use, purpose, and functionality. Much of this will not be immediately apparent to evaluators, in particular to those from outside the development team. In some cases it is also not possible to exhaustively identify and list all functionality, types of web pages, and technologies used to realize the website and its applications. The initial exploration carried out in this step is typically refined in the later steps Step 3: Select a Representative Sample and Step 4: Audit the Selected Sample, as the evaluator learns more about the target website. Involvement of website owners and website developers can help evaluators make their explorations more effective.
Note: Carrying out initial cursory checks during this step helps identify web pages that are relevant for more detailed evaluation later on. For example, an evaluator may identify web pages that seem to be lacking color contrast, document structure, or consistent navigation, and note them down for more detailed evaluation later on.
Note: To carry out this step it is critical that the evaluator has access to all the relevant parts of the website. For example, it may be necessary to create accounts or otherwise provide access to restricted areas of a website that are part of the evaluation. Granting evaluators such access may require particular security and privacy precautions.
Methodology Requirement 2.a: Identify the common web pages, which may be web page states, of the target website.
Explore the target website to identify its common web pages, which may also be web page states in web applications. Typically these are linked directly from the main entry point (home page) of the target website, and often linked from the header, navigation, and footer sections of other web pages. The outcome of this step is a list of all common web pages.
Methodology Requirement 2.b: Identify an initial list of essential functionality of the target website.
Explore the target website to identify its essential functionality. While some functionality will be easy to identify, others will need more deliberate discovery. For example, it may be easier to identify the functionality for purchasing products in an online shop than the functionality provided for vendors to sell products through the shop. The outcome of this step is a list of functionality that users can perform on the website.
Note: The purpose of this step is not to exhaustively identify all functionality of a website but to determine those that are essential to the purpose and goal of the target website. This will inform later selection of web pages and their evaluation. Other functionality will also be included in the evaluation but through other selection mechanisms.
Some examples of website functionality include:
Methodology Requirement 2.c: Identify the types of web pages and web page states.
Web pages and web page states with varying styles, layouts, structures, and functionality often have varying support for accessibility. They are also often generated by different templates and scripts, or authored by different people. They may also appear differently, behave differently, and contain different content depending on the particular website user and context. The outcome of this step is a list of the different types (as opposed to specific instances) of web pages and web page states that appear on the target website.
Content to look for to identify different types of web page and web page states include:
Methodology Requirement 2.d: Identify the web technologies relied upon to provide the website.
During this step the web technologies relied upon (for conformance) to provide the website are identified. This includes base web technologies such as HTML and CSS, auxiliary web technologies such as JavaScript and WAI-ARIA, as well as specific web technologies such as SMIL, SVG and PDF. The outcome of this step is a list of technologies that are relied upon according to WCAG 2.0.
Note: Where possible, it is often also useful to identify the libraries and components used to create the website, such as Dojo, JQuery, and others. Particularly for web applications, much of the accessibility support is built into these libraries and components, and evaluation can become more effective and efficient when these are identified.
Methodology Requirement 3.c: Identify other web pages and web page states that are relevant to people with disabilities and to accessibility of the website.
Some websites include web pages and web page states that are specifically relevant for people with disabilities and accessibility of the website. The outcome of this step is a list of such web pages. This includes:
[Review Note: Comments on this section is particularly welcome. Specifically these questions:
Other observations on this section are equally welcome.]
Methodology Requirement 3: Select a representative sample of web pages from the website according to Methodology Requirement 3.a, Methodology Requirement 3.b, Methodology Requirement 3.c, Methodology Requirement 3.d, and Methodology Requirement 3.e.
During this step the evaluator selects a sample of web pages and web page states that is representative of the target website to be evaluated. The purpose of this selection is to ensure that the evaluation results reflect the accessibility performance of the website with reasonable confidence. In cases where it is feasible to evaluate all web pages, this sampling procedure can be skipped and the selected sample is considered to be the entire website in the remaining steps of the conformance evaluation procedure.
The actual size of sample web pages and web page states needed to evaluate a website depends on many factors including:
This step relies initially on the exploration carried out in Step 2: Explore the Target Website and is continually refined during the later Step 4: Audit the Selected Sample, as the evaluator learns more about the particular implementation aspects of the target website.
Methodology Requirement 3.a: Include all common web pages, including web page states, into the selected sample.
Include all common web pages and web page states that were identified in Step 2.a: Identify Common Web Pages of the Website into the selected sample for evaluation.
Methodology Requirement 3.b: Include all other web pages and web page states that are relevant to people with disabilities and accessibility of the website into the selected sample.
Include all other relevant web pages and web page states that were identified in Step 2.e: Identify Other Relevant Web Pages into the selected sample for evaluation.
Methodology Requirement 3.c: Include instances of web pages and web page states (where applicable and available) to cover the (1) essential functionality, (2) types of web pages, and (3) web technologies relied upon into the selected sample.
Select additional instances of web pages and web pages states to ensure that the sample includes:
Some of the content might already be reflected in the web pages and web page states selected in Step 3.a: Include Common Web Pages of the Website and Step 3.b: Include Other Relevant Web Pages. For example, the common web pages might use the same web technologies and design as the majority of other web pages on the website. The number of required instances of web pages and web page states depends on the particular aspects of the website (see factors influencing the sample size).
Note: An individual web page or web page state may reflect more than one of each of these listed criteria. For example, a single web page may be representative of a particular design layout, functionality, and web technologies used. The purpose of this step is to have sufficient representation of the different types of web pages and web page states, functionality, and web technologies that occur on the website. Careful selection of these representative instances can significantly reduce the required sample size while maintaining appropriate representation of the entire website.
Methodology Requirement 3.d: Include all web pages and web page states that are part of a complete process into the selected sample.
The selected sample has to include all web pages and web page states that belong to a series presenting a complete process. No web page or web page state in the selected sample may be part of a process without all other web pages and web page states that are part of that process to be also included into the selected sample.
Use the following steps to include the necessary web pages and web page states into the sample:
Note: In most cases it is necessary to record and specify the actions needed to proceed from one web page and web page state to the next in a sequence to complete a process so that they can be replicated later. An example of such action could be "fill out name and address, and select the 'Submit' button". In most cases the web address (URI will not be sufficient to identify the web page and web page state in a complete process. It is also useful to clearly record when web pages and web page states are part of a process so that evaluators can focus their effort on the relevant changes such as elements that were added, modified, or made visible.
Methodology Requirement 3.e: Select a random sample of web pages and web page states, and include them for auditing.
A randomly selected sample of web pages and web page states acts as an indicator to verify that the structured sample selected through the previous steps truly reflects the accessibility performance of the website. Confidence in the overall evaluation outcome increases when the evaluation results from both selection approachs correlate.
The number of web pages and web page states to randomly select is 10% of the structured sample selected through the previous steps, with a minimum of 5 instances of web pages and web page states. For example, if the structured sample resulted in 80 web pages and web page states, then the random sample size is 8 web pages and web page states. For structured samples of size 50 and below the random sample size is always 5 web pages and web page states (if the website is not smaller than that).
To perform this selection, randomly select unique instances of web pages and web page states from the target website and that are not already part of the structured sample selected through the previous steps. Depending on the type of website and the access that an evaluator has for it there are different techniques that may need to be used for this selection. This may include:
Document the web pages and web page states that were randomly selected as these will need to be compared to the remaining structured sample in Step 4.e: Compare Structured and Random Samples.
Note: While the random sample need not be selected according to strictly scientific criteria, the scope of the selection needs to span the entire scope of the website (any web page and web page state on the website may be selected with similarly equivalent likelihood), and the selection of individual web page and web page states does not follow a predictable pattern. Recording the method used to generate the random sample is important for replicability and reliability of the results.
Methodology Requirement 4: Audit the selected sample of web pages according to Methodology Requirement 4.a, Methodology Requirement 4.b, Methodology Requirement 4.c, Methodology Requirement 4.d and Methodology Requirement 4.e.
During this step the evaluator audits (detailed evaluation) the sample selected in Step 3: Select a Representative Sample according to the five WCAG 2.0 conformance requirements at the conformance level from Step 1.b: Define the Conformance Target. Many web pages and web page states in the sample will have components, such as the header, navigation bars, search form, and others that are occur repeatedly. Typically these components do not need to be re-evaluated on each occurrence unless they appear or behave differently, or when additional requirements are defined in Step 1.d: Define Additional Requirements for Evaluation (Optional).
Important: Carrying out this step requires deep understanding of the WCAG 2.0 conformance requirements and the WCAG 2.0 Layers of Guidance. Understanding Conformance provides more guidance.
Note: If there is no content related to Success Criteria presented to the user (for example, no video on the web page), then the Success Criteria are "satisfied" according to WCAG 2.0. Optionally, an evaluation report can specifically indicate Success Criteria for which there is no relevant content, for example, with "not present".
Methodology Requirement 4.a: Check that each full page (web page and web page state) in the selected sample satisfies each of the WCAG 2.0 Success Criteria of the target conformance level.
For each web page and web page state in the sample selected in Step 3: Select a Representative Sample that is not within or the end of a complete process, check its conformance with each WCAG 2.0 Success Criterion within the target conformance level set in Step 1.b: Define the Conformance Target. This includes all components of the web page or web page state without activating any functions, entering any data, or otherwise interacting with the content (this will be evaluated in the subsequent steps).
Consider the following approach for evaluating the conformance of all content to each WCAG 2.0 Success Criterion:
Note: W3C/WAI continually documents (non-normative) failures and techniques for WCAG 2.0 but these can never be exhaustive to cover every possible situation. They are also not the only ways to meet or to fail to meet WCAG 2.0 Success Criteria, and evaluators typically use additional methods to evaluate conformance to WCAG 2.0 (see also Step 1.d: Define Evaluation Methods to be Used).
Note: While it is important to check the conformance of each web page and web page state in the sample to each WCAG 2.0 Success Criterion, repeated components such as the header, navigation bars, search form, and others usually do not need to be re-evaluated on each occurrence. For example, if the same header code is used on two web pages then it is evaluated on the first only in most situations.
Methodology Requirement 4.b: Check that all interaction of each web page and web page state along a complete process satisfies each of the WCAG 2.0 Success Criteria of the target conformance level.
For each complete process selected in Step 3.d: Include Complete Processes in the Sample, follow the identified default and branch sequences of web pages and web page states, and evaluate each according to Step 4.a: Check WCAG 2.0 Success Criteria. However, in this case it is not necessary to evaluate all content but only the content that changes along the process.
Functionality, entering data, notifications, and other interaction is part of this check. In particular it includes:
Methodology Requirement 4.c: Check that each web page and web page state in the selected sample that does not conform to WCAG 2.0 at the target conformance level has a conforming alternate version.
For each of the web pages and web page states in the sample (selected in Step 3: Select a Representative Sample) that does not satisfy any of the five WCAG 2.0 conformance requirements at the conformance target defined in Step 1.b: Define the Conformance Target, check that it has at least one conforming alternate version as defined in WCAG 2.0. The WCAG 2.0 guidance on Understanding Conforming Alternate Versions provides more background on accessible alternatives.
Methodology Requirement 4.d: Check that each web page and web page state in the selected sample satisfies the WCAG 2.0 conformance requirement non-interference.
For each of the web pages and web page states in the sample (selected in Step 3: Select a Representative Sample), check that it satisfies the WCAG 2.0 conformance requirement non-interference. The WCAG 2.0 guidance on Understanding Requirement 5 provides more background on non-interference.
Methodology Requirement 4.e: Check that each web page and web page state in the randomly selected sample does not show types of content and outcomes that are not represented in the structured sample.
While the individual occurences of WCAG 2.0 Success Criteria will vary between the structured and randomly selected samples, the randomly selected sample should not show new types of content not present in the structured sample. Also the outcomes from evaluating the randomly selected sample should not show new findings to those of the structured sample. If the randomly selected sample shows new types of content or new evaluation findings then it is an indication that the structured sample was not sufficiently representative of the content provided on the website. In this case evaluators need to go back to Step 3: Select a Representative Sample) to select additional web pages and web page states that reflect the newly identified types of content and findings. Also the findings of Step 2: Explore the Target Website might need to be adjusted accordingly. This step is repeated until the structured sample is adequately representative of the content provided on the website.
Methodology Requirement 5: Document the evaluation findings according to Methodology Requirement 5.a and optionally Methodology Requirement 5.b, Methodology Requirement 5.c, Methodology Requirement 5.d, and Methodology Requirement 5.e.
While evaluation findings are reported at the end of the process, recording them is carried out throughout the evaluation process to ensure reliable outcomes. The recordings typically have varying levels of confidentiality. For example, recording the specific methods used to evaluate individual requirements might remain limited to the evaluator while reports about the outcomes from these checks are typically made available to the evaluation commissioner. Website owners might further choose to make public statements about the outcomes from evaluation according to this methodology.
[Review Note: Feedback on this section is particularly welcome. Specifically, how elaborate does this documentation need to be to ensure transparency yet practicality of the methodology?]
Methodology Requirement 5.a: Document each outcome of the steps defined in Step 1: Define the Evaluation Scope, Step 2: Explore the Target Website, Step 3: Select a Representative Sample, and Step 4: Audit the Selected Sample.
Documenting the outcomes for each of the previous steps (including all sub-sections) is essential to ensure transparency of the evaluation process, replicability of the evaluation results, and justification for any statements made based on this evaluation. This documentation does not need to be public (the level of confidentiality is usually determined by the evaluation commissioner).
Documenting the outcomes for each step includes at least the following:
Note: Depending on the desired granularity of the report documentation, the outcomes of Step 4: Audit the Selected Sample can be aggregated over the entire sample. That is, for every WCAG 2.0 Success Criterion applicable (according to Step 1.b. Define the Conformance Target) and the remaining four WCAG 2.0 conformance requirements, the evaluator indicates whether each is met on every web page and web page state in the sample (selected in Step 3: Select a Representative Sample), or provides at least one example for each conformance requirement and WCAG 2.0 Success Criterion not met (without having an accessible alternative).
Depending on any additional evaluation requirements established in Step 1.e: Define Additional Evaluation Requirements (Optional) there may be additional evaluation outcomes to report. For example, an evaluation commissioner may request a report indicating every failure occurrence for every web page and web page state in the selected sample, more information about the nature and the causes of the identified failures, or repair suggestions to remedy the failures.
Methodology Requirement 5.b: Archive the web pages and web page states audited, and record the evaluation tools, web browsers, assistive technologies, other software, and methods used to audit them (Optional).
While optional, it is good practice for evaluators to keep record of the evaluation specifics, for example to support conflict resolution in the case of dispute. This includes archiving the web pages and web page states audited, and recording the evaluation tools, web browsers, assistive technologies, other software, and methods used to audit them. This recording is typically kept internal and not shared by the evaluator unless otherwise agreed on in Step 1.e: Define Additional Evaluation Requirements (Optional).
Records of the evaluation specifics could include any of the following:
This recording may apply globally for the entire evaluation, to individual web pages, or to individual checks carried out within the audited web pages and web page states. A table or grid may be useful to record what was used for the different web pages and web page states audited.
Note: Records of the evaluation specifics may include sensitive information such as internal code, passwords, and copies of data. They may need particular security and privacy precautions.
Methodology Requirement 5.c: Provide an statement describing the outcomes of the conformance evaluation (Optional).
Reminder: In the majority of situations, using this methodology alone does not result into WCAG 2.0 conformance claims for the target websites; see Relation to WCAG 2.0 Conformance Claims for more background.
Website owners may wish to make public statements about the outcomes from evaluations following this methodology. This can be done when at least every non-optional methodology requirement is satisifed, the conformance target defined in Step 1.b. Define the Conformance Target is satisfied by all web pages and web page states audited (in Step 4: Audit the Selected Sample), and the website owner commits to ensuring the validty and maintaining the accuracy of the evaluation statement made.
An evaluation statement according to this methodology includes at least the following information:
Evaluation statements according to this methodology can also be made when only partial conformance to WCAG 2.0 has been achieved. In such cases the evaluation statements have to also include the following information:
[Review Note: Feedback on this section is particularly welcome. Specifically, how useful is the aggregated score for you, for example, to help communicate progress over time to website owners? What suggestions do you have for improving the concept of a score in this methodology.]
Methodology Requirement 5.d: Provide an Aggregated score (Optional).
While aggregated scores provide a numerical indicator to help communicate progress over time, there is currently no single widely recognized metric that reflects the required reliability, accuracy, and practicality. In fact, aggregated scores can be misleading and do not provide sufficient context and information to understand the actual accessibility of a website. A [Draft] W3C Research Report on Web Accessibility Metrics provides more background for different approaches and limitations of scoring metrics.
This methodology proposes two simple scoring approaches to select from. Other scoring mechanisms can be used as well. In any case, the scoring approach used has to be clearly indicated along with the score whenever such a score is provided. It is also recommended that the scoring approach is documented and made available to the evaluation commissioner along with the report to facilitate transparency and repeatability.
This score calculates a ratio over the collective sample. That is, WCAG 2.0 Success Criteria are counted once for the entire sample as follows:
This particular score sensitive towards failures but insensitive towards their relative frequency. Specifically, a failure to satisfy any WCAG 2.0 Success Criterion on any web page or web page state in the sample is directly reflected in the count. However, recurring failures do not influence the count any further.
This score calculates a ratio over the individual web pages. That is, WCAG 2.0 Success Criteria are counted on every web page in the sample as follows:
This particular score is more sensitive towards the frequency of failures but requires more effort to calculate. For example, a single occurence of a failure will have smaller effect on the score while repeated failures will have stronger effect. However, the score does not consider the relative impact of the failures on accessibility. For example, a single failure will yield a high score even if that one failire is an inaccessible CAPTCHA that prevents access to the entire website.
Methodology Requirement 5.e: Provide machine-readable reports of the evaluation results (Optional).
Machine-readable reports facilitate processing the evaluation results by authoring, web accessibility evaluation tools, and quality assurance tools. The Evaluation and Report Language (EARL) is a machine-readable format that was specifically designed for this purpose. It is recommended to use EARL for providing machine-readable reports. See also Understanding Metadata from WCAG 2.0 to learn more about uses of metadata, including machine-readable reports, such as EARL.
Past and present active participants of the WCAG 2.0 Evaluation Methodology Task Force (Eval TF) include: Shadi Abou-Zahra; Frederick Boland; Denis Boudreau; Amy Chen; Vivienne Conway; Bim Egan; Michael Elledge; Gavin Evans; Wilco Fiers; Detlev Fischer; Elizabeth Fong; Vincent François; Alistair Garrison; Emmanuelle Gutiérrez y Restrepo; Katie Haritos-Shea; Martijn Houtepen; Peter Korn; Maureen Kraft; Aurelien Levy; David MacDonald; Mary-Jo Mueller; Donald Raikes; Corominas Ramon; Roberto Scano; Samuel Sirois; Sarah J Swierenga; Eric Velleman; Konstantinos Votis; Kathleen Wahlbin; Elle Waters; Richard Warren; Léonie Watson.
Changes since the Public Working Draft of 26 February 2013 are documented in: