> For the complete documentation index, see [llms.txt](https://qatesting.gitbook.io/qa/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://qatesting.gitbook.io/qa/accessibility-testing/wcag-principles/understandable.md).
# Understandable
### Understandable ๐ก๐
Information and UI must be **understandable**:
* Make text readable and understandable ๐
* Make content appear predictable ๐
* Help users avoid and correct mistakes ๐ซโก๏ธโ
#### Guideline 3.1 Readable[ยง](https://www.w3.org/TR/WCAG21/#readable)
Make text content readable and understandable.
**Success Criterion 3.1.1 Language of Page**[**ยง**](https://www.w3.org/TR/WCAG21/#language-of-page)
[Understanding Language of Page](https://www.w3.org/WAI/WCAG21/Understanding/language-of-page.html) |\
[How to Meet Language of Page](https://www.w3.org/WAI/WCAG21/quickref/#language-of-page)
(Level A)
The default [human language](https://www.w3.org/TR/WCAG21/#dfn-human-language-s) of each [Web page](https://www.w3.org/TR/WCAG21/#dfn-web-page-s) can be [programmatically determined](https://www.w3.org/TR/WCAG21/#dfn-programmatically-determinable).
**Success Criterion 3.1.2 Language of Parts**[**ยง**](https://www.w3.org/TR/WCAG21/#language-of-parts)
[Understanding Language of Parts](https://www.w3.org/WAI/WCAG21/Understanding/language-of-parts.html) |\
[How to Meet Language of Parts](https://www.w3.org/WAI/WCAG21/quickref/#language-of-parts)
(Level AA)
The [human language](https://www.w3.org/TR/WCAG21/#dfn-human-language-s) of each passage or phrase in the content can be [programmatically determined](https://www.w3.org/TR/WCAG21/#dfn-programmatically-determinable) except for proper names, technical terms, words of indeterminate language, and words or phrases that have become part of the vernacular of the immediately surrounding text.
**Success Criterion 3.1.3 Unusual Words**[**ยง**](https://www.w3.org/TR/WCAG21/#unusual-words)
[Understanding Unusual Words](https://www.w3.org/WAI/WCAG21/Understanding/unusual-words.html) |\
[How to Meet Unusual Words](https://www.w3.org/WAI/WCAG21/quickref/#unusual-words)
(Level AAA)
A [mechanism](https://www.w3.org/TR/WCAG21/#dfn-mechanism) is available for identifying specific definitions of words or phrases [used in an unusual or restricted way](https://www.w3.org/TR/WCAG21/#dfn-used-in-an-unusual-or-restricted-way), including [idioms](https://www.w3.org/TR/WCAG21/#dfn-idioms) and [jargon](https://www.w3.org/TR/WCAG21/#dfn-jargon).
**Success Criterion 3.1.4 Abbreviations**[**ยง**](https://www.w3.org/TR/WCAG21/#abbreviations)
[Understanding Abbreviations](https://www.w3.org/WAI/WCAG21/Understanding/abbreviations.html) |\
[How to Meet Abbreviations](https://www.w3.org/WAI/WCAG21/quickref/#abbreviations)
(Level AAA)
A [mechanism](https://www.w3.org/TR/WCAG21/#dfn-mechanism) for identifying the expanded form or meaning of [abbreviations](https://www.w3.org/TR/WCAG21/#dfn-abbreviations) is available.
**Success Criterion 3.1.5 Reading Level**[**ยง**](https://www.w3.org/TR/WCAG21/#reading-level)
[Understanding Reading Level](https://www.w3.org/WAI/WCAG21/Understanding/reading-level.html) |\
[How to Meet Reading Level](https://www.w3.org/WAI/WCAG21/quickref/#reading-level)
(Level AAA)
When text requires reading ability more advanced than the [lower secondary education level](https://www.w3.org/TR/WCAG21/#dfn-lower-secondary-education-level) after removal of proper names and titles, [supplemental content](https://www.w3.org/TR/WCAG21/#dfn-supplementary-content), or a version that does not require reading ability more advanced than the lower secondary education level, is available.
**Success Criterion 3.1.6 Pronunciation**[**ยง**](https://www.w3.org/TR/WCAG21/#pronunciation)
[Understanding Pronunciation](https://www.w3.org/WAI/WCAG21/Understanding/pronunciation.html) |\
[How to Meet Pronunciation](https://www.w3.org/WAI/WCAG21/quickref/#pronunciation)
(Level AAA)
A [mechanism](https://www.w3.org/TR/WCAG21/#dfn-mechanism) is available for identifying specific pronunciation of words where meaning of the words, in context, is ambiguous without knowing the pronunciation.
#### Guideline 3.2 Predictable[ยง](https://www.w3.org/TR/WCAG21/#predictable)
Make Web pages appear and operate in predictable ways.
**Success Criterion 3.2.1 On Focus**[**ยง**](https://www.w3.org/TR/WCAG21/#on-focus)
[Understanding On Focus](https://www.w3.org/WAI/WCAG21/Understanding/on-focus.html) |\
[How to Meet On Focus](https://www.w3.org/WAI/WCAG21/quickref/#on-focus)
(Level A)
When any [user interface component](https://www.w3.org/TR/WCAG21/#dfn-user-interface-components) receives focus, it does not initiate a [change of context](https://www.w3.org/TR/WCAG21/#dfn-change-of-context).
**Success Criterion 3.2.2 On Input**[**ยง**](https://www.w3.org/TR/WCAG21/#on-input)
[Understanding On Input](https://www.w3.org/WAI/WCAG21/Understanding/on-input.html) |\
[How to Meet On Input](https://www.w3.org/WAI/WCAG21/quickref/#on-input)
(Level A)
Changing the setting of any [user interface component](https://www.w3.org/TR/WCAG21/#dfn-user-interface-components) does not automatically cause a [change of context](https://www.w3.org/TR/WCAG21/#dfn-change-of-context) unless the user has been advised of the behavior before using the component.
**Success Criterion 3.2.3 Consistent Navigation**[**ยง**](https://www.w3.org/TR/WCAG21/#consistent-navigation)
[Understanding Consistent Navigation](https://www.w3.org/WAI/WCAG21/Understanding/consistent-navigation.html) |\
[How to Meet Consistent Navigation](https://www.w3.org/WAI/WCAG21/quickref/#consistent-navigation)
(Level AA)
Navigational mechanisms that are repeated on multiple [Web pages](https://www.w3.org/TR/WCAG21/#dfn-web-page-s) within a [set of Web pages](https://www.w3.org/TR/WCAG21/#dfn-set-of-web-pages) occur in the [same relative order](https://www.w3.org/TR/WCAG21/#dfn-same-relative-order) each time they are repeated, unless a change is initiated by the user.
**Success Criterion 3.2.4 Consistent Identification**[**ยง**](https://www.w3.org/TR/WCAG21/#consistent-identification)
[Understanding Consistent Identification](https://www.w3.org/WAI/WCAG21/Understanding/consistent-identification.html) |\
[How to Meet Consistent Identification](https://www.w3.org/WAI/WCAG21/quickref/#consistent-identification)
(Level AA)
Components that have the [same functionality](https://www.w3.org/TR/WCAG21/#dfn-same-functionality) within a [set of Web pages](https://www.w3.org/TR/WCAG21/#dfn-set-of-web-pages) are identified consistently.
**Success Criterion 3.2.5 Change on Request**[**ยง**](https://www.w3.org/TR/WCAG21/#change-on-request)
[Understanding Change on Request](https://www.w3.org/WAI/WCAG21/Understanding/change-on-request.html) |\
[How to Meet Change on Request](https://www.w3.org/WAI/WCAG21/quickref/#change-on-request)
(Level AAA)
[Changes of context](https://www.w3.org/TR/WCAG21/#dfn-change-of-context) are initiated only by user request or a [mechanism](https://www.w3.org/TR/WCAG21/#dfn-mechanism) is available to turn off such changes.
#### Guideline 3.3 Input Assistance[ยง](https://www.w3.org/TR/WCAG21/#input-assistance)
Help users avoid and correct mistakes.
**Success Criterion 3.3.1 Error Identification**[**ยง**](https://www.w3.org/TR/WCAG21/#error-identification)
[Understanding Error Identification](https://www.w3.org/WAI/WCAG21/Understanding/error-identification.html) |\
[How to Meet Error Identification](https://www.w3.org/WAI/WCAG21/quickref/#error-identification)
(Level A)
If an [input error](https://www.w3.org/TR/WCAG21/#dfn-input-error) is automatically detected, the item that is in error is identified and the error is described to the user in text.
**Success Criterion 3.3.2 Labels or Instructions**[**ยง**](https://www.w3.org/TR/WCAG21/#labels-or-instructions)
[Understanding Labels or Instructions](https://www.w3.org/WAI/WCAG21/Understanding/labels-or-instructions.html) |\
[How to Meet Labels or Instructions](https://www.w3.org/WAI/WCAG21/quickref/#labels-or-instructions)
(Level A)
[Labels](https://www.w3.org/TR/WCAG21/#dfn-labels) or instructions are provided when content requires user input.
**Success Criterion 3.3.3 Error Suggestion**[**ยง**](https://www.w3.org/TR/WCAG21/#error-suggestion)
[Understanding Error Suggestion](https://www.w3.org/WAI/WCAG21/Understanding/error-suggestion.html) |\
[How to Meet Error Suggestion](https://www.w3.org/WAI/WCAG21/quickref/#error-suggestion)
(Level AA)
If an [input error](https://www.w3.org/TR/WCAG21/#dfn-input-error) is automatically detected and suggestions for correction are known, then the suggestions are provided to the user, unless it would jeopardize the security or purpose of the content.
**Success Criterion 3.3.4 Error Prevention (Legal, Financial, Data)**[**ยง**](https://www.w3.org/TR/WCAG21/#error-prevention-legal-financial-data)
[Understanding Error Prevention (Legal, Financial, Data)](https://www.w3.org/WAI/WCAG21/Understanding/error-prevention-legal-financial-data.html) |\
[How to Meet Error Prevention (Legal, Financial, Data)](https://www.w3.org/WAI/WCAG21/quickref/#error-prevention-legal-financial-data)
(Level AA)
For [Web pages](https://www.w3.org/TR/WCAG21/#dfn-web-page-s) that cause [legal commitments](https://www.w3.org/TR/WCAG21/#dfn-legal-commitments) or financial transactions for the user to occur, that modify or delete [user-controllable](https://www.w3.org/TR/WCAG21/#dfn-user-controllable) data in data storage systems, or that submit user test responses, at least one of the following is true:
Reversible
Submissions are reversible.
Checked
Data entered by the user is checked for input errors and the user is provided an opportunity to correct them.
Confirmed
A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission.
**Success Criterion 3.3.5 Help**[**ยง**](https://www.w3.org/TR/WCAG21/#help)
[Understanding Help](https://www.w3.org/WAI/WCAG21/Understanding/help.html) |\
[How to Meet Help](https://www.w3.org/WAI/WCAG21/quickref/#help)
(Level AAA)
[Context-sensitive help](https://www.w3.org/TR/WCAG21/#dfn-context-sensitive-help) is available.
**Success Criterion 3.3.6 Error Prevention (All)**[**ยง**](https://www.w3.org/TR/WCAG21/#error-prevention-all)
[Understanding Error Prevention (All)](https://www.w3.org/WAI/WCAG21/Understanding/error-prevention-all.html) |\
[How to Meet Error Prevention (All)](https://www.w3.org/WAI/WCAG21/quickref/#error-prevention-all)
(Level AAA)
For [Web pages](https://www.w3.org/TR/WCAG21/#dfn-web-page-s) that require the user to submit information, at least one of the following is true:
Reversible
Submissions are reversible.
Checked
Data entered by the user is checked for input errors and the user is provided an opportunity to correct them.
Confirmed
A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission.