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Operable

This article provides practical advice on how to write your web content so that it conforms to the success criteria outlined in the Operable principle of the Web Content Accessibility Guidelines (WCAG) 2.0. Operable states that user interface components and navigation must be operable.

Note: To read the original W3C definitions for Operable and its guidelines and success criteria, see Principle 2: Operable — User interface components and navigation must be operable.

Guideline 2.1 — Keyboard Accessible: Make all functionality available from a keyboard

This guideline covers the necessity of making core website functionality available via a keyboard in addition to other means (e.g. mouse), so that users that rely on keyboard controls can access them.

Success criteria How to conform to the criteria Practical resource
2.1.1 Keyboard (A) All functionality should be accessible using keyboard controls, unless it cannot be done using the keyboard (e.g. freehand drawing). Built-in controls should be used where possible (e.g. tabbing through form controls), and you should only build in custom functionality where needed. See UI controls and Building keyboard accessibility back in
2.1.2 No keyboard trap (A)

When entering a section of functionality using the keyboard, you should be able to get out of that section again using *only* the keyboard. For example, if you press Enter/Return on a focused button to open an options window, you should be able to close that window again and return to the main content using the keyboard.

This is very important so that keyboard users do not get trapped on specific sections of your apps.

 
2.1.3 Keyboard — all functionality (AAA) This is a further step beyond criterion 2.1.1. To achieve AAA conformance, all functionality should be accessible using keyboard controls — with no exceptions. See UI controls and Building keyboard accessibility back in

Guideline 2.2 — Enough Time: Provide users enough time to read and use content

This guideline covers situations in which functionality may have a time limit. For example, purchases sometimes need to be completed within a time limit for security reasons.

Success criteria How to conform to the criteria Practical resource
2.2.1 Timing is adjustable (A)

For functionality with time limits (e.g. completing a hotel or flight booking often has a time limit), the user should be given controls to allow them to adjust, extend or turn off the time limit.

Exceptions to this are activities with time limits longer than 20 hours, real time events (e.g. live multiplayer games), and any other activity that requires a time limit and would be invalidated if it were turned off.

 
2.2.2 Pausing, stopping, hiding (A)

For moving/blinking content that starts automatically, lasts longer than 5 seconds, and is shown alongside other content, controls should be provided to pause, stop, or hide it. This does not apply to moving/blinking content that is essential to the experience. Examples include scrolling text and videos.

For auto-updating information that starts automatically and is shown alongside other content, controls should be provided to pause, stop, or hide it, or to control the frequency of updates. This does not apply to auto-updating content that is essential to the experience. Examples include carousels or rotating annoucements.

 
2.2.3 No time limits (AAA) This builds on criteria 2.2.1, stating that content that wants to pass AAA conformance should have no time limits.  
2.2.4 Surpress interruptions (AAA) Any interruptions such as alerts or interstitial adverts should have functionality available to suppress or postpone them, unless it is an emergency alert.  
2.2.5 Re-authenticating If an authentication session expires during usage of a web app, the user can re-authenticate and continue their usage without losing any data.  

Note: Also see the original WCAG description for Guideline 2.2 Enough Time: Provide users enough time to read and use content.

Guideline 2.3 — Seizures: Do not design content in a way that is known to cause seizures

This refers to content that, if not changed, could cause seizures in users with conditions such as epilepsy.

Success criteria How to conform to the criteria Practical resource
2.3.1 Three flashes, or below threshold (A) Content doesn't contain any aspect that Flashes more than three times per second, or flashing content is below acceptable flash and red flash thresholds.  
2.3.2 Three flashes (AAA) Content doesn't contain any aspect that Flashes more than three times per second.  

Guideline 2.4 — Navigable: Provide ways to help users navigate, find content, and determine where they are

The conformance criteria under this guideline relate to ways in which users can be expected to orientate themselves, and find the content and functionality they are looking for on the current page or other pages of the site.

Success criteria How to conform to the criteria Practical resource
2.4.1 Bypass blocks (A)

A mechanism should be provided that allows the user to skip straight to the main content or functionality available on the page, past the repeated features (such as the company logo or navigation). This is often achieved using "skip links" — links put at the top of the page source that link to the main content and are hidden by CSS.

If a proper structure of headings and semantic containers is provided to navigate with (for example <section>, <aside>, etc.), then an added "skip link" is not needed.

Need to add a section on "skip links".
2.4.2 Include page title (A) Each web page should include an informative <title>, the content of which describes the page's content/purpose. See Adding a title.
2.4.3 Logical focus order (A) The "tabbing order" of focusable page features (e.g. links, buttons, form inputs) makes logical sense, meaning that the page is still usable by non-sighted/keyboard users. See UI controls for general advice on tabbing to controls. If you need to place elements in an unusual layout, it is better to make sure the source order is sensible, then use CSS features like positioning to handle the layout. 
2.4.4 Link purpose (in context) (A) The purpose/destination of a link can be determined from the link text, or from its surroundings (e.g. the surrounding text). Exceptions are where the link purpose is ambiguous to all users (see ambiguous to users in general for a useful explanation of this). See Meaningful text labels. Also note that you should minimize instances where multiple copies of the same text are linked to different places. This can cause problems for screenreader users, who will often bring up a list of the links out of context — several links all labelled "click here", "click here", "click here" would be confusing.
2.4.5 Multiple navigation mechanisms (AA)

You should provide at least two general navigation mechanisms to find pages on your web site, for example navigation menu, breadcrumb trail, site search, site map, list of related links, etc.

The only exception to this is where a page is one step in a process, so should only logically have links to the previous and next steps.

Most of these mechanisms can be created using simple HTML features, for example see Search field, Creating a navigation menu, Styling links as buttons.
2.4.6 Headings and labels (AA) Heading (e.g. <h2>) and <label> elements clearly describe the purpose of the content and form elements they are supposed to be describing.

See UI controls, Meaningful text labels, The basics of headings and paragraphs, The <label> element.

Note that you should avoid duplicating headings or labels (e.g. multiple instances of "Further information"), unless the structure allows you to differentiate between them easily.

2.4.7 Visible focus for focusable elements (AA) When tabbing through focusable elements such as links or form inputs, there should be a visual indicator to show you which element currently has focus. This is usually a dotted or blue outline by default (depending on browser, platform, etc.), but this can be overidden by CSS. See Using native keyboard accessibility.
2.4.8 Location within site (AAA) When on a page inside a complex site or set of steps, the user should be given an indicator of where they are in the site, for example a breadcrumb trail, sitemap or text such as "Form page 2 of 10".  
2.4.9 Link purpose (link only) (AAA) This criterion builds on 2.4.4, stating that to conform to AAA, the purpose/destination of a link should be determinable from the link text alone, even if out of context. See Meaningful text labels. Also note that you should minimize instances where multiple copies of the same text are linked to different places. This can cause problems for screenreader users, who will often bring up a list of the links out of context — several links all labelled "click here", "click here", "click here" would be confusing.
2.4.10 Section headings (AAA)

As well as creating a useful document structure, headings should also accurately describe and break up content areas into logical sections.

Note that this criterion refers to headings and titles in general web content (e.g. headings within text content). Headings and titles for user interfaces are a special case covered in criterion 4.1.2.

See The basics of headings and paragraphs.

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