Web Accessibility: Important optimization for AI crawlers

1. ARIA or title attribute on interactive elements
2. Alternative text (alt or aria-label) on each image
3. Label associated with each form field
4. Sufficient contrast (text/background)
5. HTML validity (tag structure, nesting)
6. Text readability (font size)

1. ARIA or title attribute on interactive elements

Interactive elements (buttons, links, form fields) must be clearly identifiable and understandable by all users, including those using assistive technologies. ARIA (Accessible Rich Internet Applications) attributes or the title attribute play a crucial role in this regard.

• Using ARIA: For complex interactive elements or custom widgets, use the aria-label, aria-labelledby, aria-describedby, or aria-haspopup attributes to provide semantic information and accessible descriptions. These attributes are essential for screen readers and other assistive tools.

<button aria-label="Close Modal Window"></button>
<div role="dialog" aria-labelledby="dialog-title" aria-describedby="dialog-description">
   <h2 id="dialog-title">Modal Title</h2>
   <p id="dialog-description">Modal Content.</p>
</div>

• Using title: The title attribute can be used to provide additional information about an element, but it should not replace ARIA attributes or visible text when the information is critical. It is useful for non-essential supplemental information.

<a href="#" title="Learn more about our privacy policy">Privacy Policy</a>

2. Alternative text (alt or aria-label) on each image

Images are important visual elements, but they should be accompanied by alternative text for users who cannot see them (for example, screen reader users or those with slow connections).

• Alt attribute: For informational images, the alt attribute on the <img> tag must contain a concise and relevant description of the image's content. This text is read by screen readers and displayed if the image fails to load.

<img src="logo.png" alt="XYZ Company Logo">

• aria-label for decorative or complex images: For purely decorative images, the alt attribute must be empty (alt=""). For complex images (charts, diagrams) that require a longer description, use aria-describedby pointing to a visible description element or aria-label if the description is short and does not need to be visible.

<img src="icone-decorative.svg" alt="">

<img src="graphique-ventes.png" alt="Annual Sales Graph" aria-describedby="description-graphe">

<p id="description-graphe">This graph shows a 15% increase in sales over the last quarter.</p>

3. Label associated with each form field

Form fields should be clearly labeled so users understand their purpose. This is crucial for accessibility and user experience.

• <label> tag: Each form field (<input>, <textarea>, <select>) must be associated with a <label> tag. using the for attribute that matches the id attribute of the form field.

<label for="name">Name:</label>

<input type="text" id="name" name="name">

• aria-label or aria-labelledby: If a visual label is not possible or the field is complex, use aria-label or aria-labelledby to provide an accessible name for the field.

<input type="search" aria-label="Search the site">

4. Sufficient Contrast (Text/Background)

Sufficient contrast between text and its background is essential for readability, especially for people with visual impairments or in difficult lighting conditions.

• WCAG Guidelines: Follow the Web Content Accessibility Guidelines (WCAG) for color contrast. For regular text, the contrast ratio should be at least 4.5:1. For large text (18pt or 14pt bold and larger), the ratio should be at least 3:1.
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• Checking Tools: Use online tools or browser extensions to check your color contrast ratios. Tools like WebAIM's Color Contrast Checker from WebAIM can help you validate your color choices.

5. HTML Validity (Tag Structure, Nesting)

Semantically correct and well-structured HTML is the foundation of good accessibility. Errors in tag structure or incorrect nesting can make content incomprehensible to assistive technologies.

• HTML Validation: Ensure your HTML is valid by using an HTML validator (e.g., the W3C Markup Validation Service). Correct all errors and warnings related to tag structure, missing or incorrect attributes, and nesting.
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• Semantic Use: Use HTML tags semantically (<header>, <nav>, <main>, <article>, <section>, <footer>, etc.) to structure your content. This helps screen readers navigate and understand the page hierarchy.

6. Text Readability (Font Size)

Font size is a direct factor in content readability. Text that is too small can be difficult for many users to read.

• Minimum font size: Make sure the font size for body text is at least 16px (or 1em/1rem). For headings and other elements, use proportionally larger, but still readable, sizes.
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• Relative units: Favor the use of relative units (em, rem, %, vw) for font sizes, which allows users to zoom in on text without breaking the layout.

Resources & Useful Links

Here are some useful resources and links to deepen your knowledge and help you implement Web Accessibility (WCAG):

• WCAG (Web Content Accessibility Guidelines) 2.1
• WebAIM's Color Contrast Checker
• W3C Markup Validation Service