For each non-time-based medium that has an alternative, is this alternative relevant?
A <canvas> displays a bar chart with quarterly results. The alternative provided: "Chart". For a screen reader user, this information is worthless. They already knew there was a chart. What criterion 4.9 requires is that the alternative convey the actual data from the media.
Criterion 4.8 checks if an alternative exists. Criterion 4.9 checks if it is usable. An alternative is relevant when it provides access to the same content and similar functionality to the non-temporal media: the values of a chart, the structure of a diagram, the information in an SVG infographic. If the user must see the media to understand what it says, the alternative has failed.
The criterion also covers a less obvious case: an image used as alternative content. If the alternative to an <object> is an <img> without alt, the accessibility chain breaks at that point. The alternative image must itself be accessible for the test to be validated.
Un test to assess the relevance of the alternative to non-temporal media
Relevance of alternative to non-temporal media
- Identify all non-temporal media in the document that have an alternative (identified via criterion 4.8: adjacent link, button, content within the element).
- For each media, read the alternative without looking at the media itself.
- Compare: does the alternative convey the same content and functionality as the media?
- If the alternative is an image, verify that it carries itself a relevant
altattribute (oraria-label). - If all alternatives are relevant, the test is validated. A single non-relevant alternative is enough to fail the test.
Examples
❌ Non-compliant : Canvas chart with generic alternative
<canvas id="ventes-chart" aria-label="Chart"></canvas>The alternative identifies the type of media, not its content. The screen reader announces "Chart" and stops there. The user does not know what data is represented. This is the most common error in audits of non-temporal media.
✅ Compliant : Canvas chart with complete alternative
<canvas id="ventes-chart" aria-label="2024 Sales by quarter: Q1 120,000 €, Q2 145,000 €, Q3 132,000 €, Q4 178,000 €. Annual growth of 48%."></canvas>The alternative conveys the actual data from the chart. A screen reader user obtains the same information as a user who sees the diagram: the quarterly values and the overall trend.
❌ Non-compliant : SVG object with alternative image without alternative text
<object data="schema-architecture.svg" type="image/svg+xml">
<img src="schema-fallback.png">
</object>The fallback image has no alt attribute. Even if it visually replaces the SVG, it is inaccessible to assistive technologies. The accessibility chain is broken: criterion 4.9 fails.
✅ Compliant : SVG object with accessible alternative image
<object data="schema-architecture.svg" type="image/svg+xml">
<img src="schema-fallback.png" alt="Architecture diagram: three tiers connected by REST APIs — presentation, business logic, database">
</object>The alternative image carries an alt that describes the content of the diagram. Whether the browser displays the SVG or the fallback image, the user accesses the same information about the architecture.
Tips and pitfalls
⚠️ Naming the element instead of describing its content
The alternatives "Chart", "Diagram" or "Infographic" appear systematically in audits. They answer "What is this?", not "What does this media say?". The alternative must convey the content, not categorize the element.
⚠️ Image used as alternative: double verification mandatory
When the alternative to an <object> or <embed> is an <img>, criterion 4.9 requires that this image be itself accessible. Verify that the <img> carries a relevant alt describing the content of the original media. This is a case explicitly covered by RGAA and often overlooked during audits.
💡 For complex charts, prefer an adjacent data table
An aria-label is limited in practical length. For a chart with dozens of values, provide an adjacent HTML table referenced via aria-describedby. It is more complete, easier to maintain, and also benefits sighted users who want the raw data.
⚠️ The criterion is only evaluated if criterion 4.8 is satisfied
If a non-temporal media has no alternative (criterion 4.8 not met), criterion 4.9 is not applicable for that element. In an audit, we first document 4.8 as non-conformant; 4.9 is not scored independently for that same element.
⚠️ Relevance does not mean exhaustiveness
The alternative does not have to reproduce every detail of the media. It must allow access to the same content and similar functionality. For a summary infographic, key points are sufficient. The true criterion of judgment: can a user without access to the media accomplish the same tasks as a user who sees it?
Frequently asked questions
What is the concrete difference between criterion 4.8 and criterion 4.9?
Criterion 4.8 asks the question of existence: is there a mechanism that provides access to an alternative (link, button, content within the element)? Criterion 4.9 asks the question of quality: does this alternative really convey the same content? We evaluate 4.9 only when 4.8 is satisfied.
How do I test the relevance of a text alternative without an automated tool?
Read the alternative without looking at the media, note what you understood, then look at the media. If you learn something the alternative did not mention, it is not relevant. This is an inescapable manual test: no automated tool can assess the relevance of content for you.
How do I determine the appropriate length of a text alternative for RGAA media?
No, length is secondary. It must be sufficient to access the same content and functionality. For a simple chart, two sentences are enough. For a complex infographic, an adjacent HTML table will be more suitable than an endless aria-label. What matters is completeness, not form.
What does RGAA verify when the alternative to a temporal media is an image?
The alternative image must carry an alt (or aria-label) that relevantly describes the content of the original media. The criterion explicitly covers this case: if the image is not accessible, the accessibility chain is broken and criterion 4.9 fails, even if the image is visually faithful to the media.
How does criterion 4.9 of RGAA apply to inline <svg> elements?
Yes, if the <svg> is treated as a non-temporal media with a text alternative (via aria-describedby pointing to a text block, for example). The alternative must describe the content of the SVG, not just name it. For <svg> carrying information as images, criterion 1.4.6 applies in parallel.