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WCAG Explorer (beta)

This resource is designed for anyone eager to master digital accessibility. Explore WCAG success criteria through clear, easy-to-understand descriptions. We owe a special "hat tip" to Johannes Lehner’s WCAG Card Deck, which served as the inspiration for this project.

We plan to expand this library over time, so please check back regularly for updates.

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  • Understandable

21 success criteria found for Understandable principle

Success criterion 3.1.1 Language of Page

Level Level A, WCAG principle: Understandable

Assigned to the following themes: CODE AND LABELS WORDING

Each page must have a <html lang=""> attribute that matches the main language of the page.

Success criterion 3.2.1 On Focus

Level Level A, WCAG principle: Understandable

Assigned to the following themes: KEYBOARD

No unexpected changes must happen when an element receives focus (like open a popup, move focus, submit a form).

Success criterion 3.2.2 On Input

Level Level A, WCAG principle: Understandable

Assigned to the following themes: CODE AND LABELS FORMS KEYBOARD

No unexpected changes must happen when a field value changes (like auto-submit, reload, open new page).

Success criterion 3.3.1 Error Identification

Level Level A, WCAG principle: Understandable

Assigned to the following themes: FORMS WORDING

Errors and validation must be clearly identified and described in text, not just visually (like color or highlighting).

Success criterion 3.3.2 Labels or Instructions

Level Level A, WCAG principle: Understandable

Assigned to the following themes: CODE AND LABELS FORMS

Form fields must have clear labels or instructions to avoid confusion and help complete the input correctly.

Success criterion 3.3.7 Redundant Entry (2.2 only)

Level Level A, WCAG principle: Understandable

Assigned to the following themes: FORMS

Don't ask for the same information twice in the same process.

Provide pre-filled fields or selection options if the information was already given.

Success criterion 3.1.2 Language of Parts

Level Level AA, WCAG principle: Understandable

Assigned to the following themes: CODE AND LABELS WORDING

Any parts of the content in a different language must be marked with the correct lang attribute.

Expressions borrowed from another language (like "déjà vu" in English) do not need this, unless pronunciation or understanding would be affected.

Success criterion 3.2.3 Consistent Navigation

Level Level AA, WCAG principle: Understandable

Assigned to the following themes: WHOLE SITE

Navigation elements (like menus, links, search) must appear in the same place and order across pages.

Success criterion 3.3.3 Error Suggestion

Level Level AA, WCAG principle: Understandable

Assigned to the following themes: FORMS WORDING

Errors and validation messages must show text that:

  • explains the problem and
  • gives suggestions for how to fix it (like "enter at least 8 characters")

Success criterion 3.1.3 Unusual Words

Level Level AAA, WCAG principle: Understandable

Assigned to the following themes: WORDING

Unusual terms, jargon, or figurative language should be:

  • avoided when possible, or
  • explained the first time they appear

Success criterion 3.1.4 Abbreviations

Level Level AAA, WCAG principle: Understandable

Assigned to the following themes: WORDING

Abbreviations and acronyms should be:

  • avoided when possible, or
  • explained the first time they appear

Success criterion 3.1.5 Reading Level

Level Level AAA, WCAG principle: Understandable

Assigned to the following themes: WORDING

If content requires reading skills above lower secondary education (around 9th grade), provide:

  • a simpler version,
  • a summary,
  • a visual aid, or
  • a spoken version

to help with understanding.

Success criterion 3.1.6 Pronunciation

Level Level AAA, WCAG principle: Understandable

Assigned to the following themes: WORDING

If a word can be pronounced in different ways with different meanings, the intended meaning must be clarified to avoid confusion or ambiguity.

Success criterion 3.2.5 Change on Request

Level Level AAA, WCAG principle: Understandable

Assigned to the following themes: FORMS KEYBOARD

Major changes (like open dialog, navigate, submit) must only happen when explicitly requested.

Success criterion 3.3.5 Help

Level Level AAA, WCAG principle: Understandable

Assigned to the following themes: FORMS WORDING

Provide additional help (like text instructions, help links, or tooltips) when label alone might be ambiguous or confusing.

Success criterion 3.3.6 Error Prevention (All)

Level Level AAA, WCAG principle: Understandable

Assigned to the following themes: FORMS WORDING

Before submitting, all forms must allow:

  • reviewing the input,
  • correcting mistakes, or
  • confirming