Do not let a symbol alone carry meaning
F26 is a documented failure under the sensory characteristics rule, and its scope is narrower than its title suggests. A graphical symbol here means a glyph that carries information without words and is not the character that already has that meaning. So a shape used as a status marker is squarely inside it, and a genuine arrow character may well sit outside it, though a link whose only content is an arrow still fails the rule on the wider ground that the instruction rests on a sensory characteristic alone. The worked example is a shopping cart using a circle for in stock and a square for back-ordered, with the instructions above the list referring to the circle and the square and nothing else. Anything that puts words on the meaning fixes it. Visible text is best. An image with a text alternative works. For an icon font the answer is an image role and a label, since a font glyph has no alt attribute to give it.
How we find it in an audit
Reviewers find the instructions first, because the published test is scoped to instructions referring to non-text marks rather than to every symbol on the page. Then each referenced mark gets checked for another route to the same information. We go wider than that in practice and inventory the icon-only controls as well, since an icon font with no accessible name is a naming problem as well as a sensory one, and it is how most sites produce this in the first place.
How affected users experience it
A screen reader announces what the accessibility tree holds. For an icon font that is often a private-use character, which arrives as nothing, or as whatever the font vendor happened to call it. For an image with no alt it is silence or a filename. Either way the user reaches a list where every row ends in the same nothing, and the instruction above the list told them to look for a circle. Someone with low vision meets the same problem at a different scale, because two small shapes that differ by a few pixels are one shape when magnified and blurred.
Passes vs. fails
Passes
<td><span class="dot circle" aria-hidden="true"></span> In stock</td>
<!-- The words carry the status. The shape is decoration now. -->Fails
<td><span class="dot circle"></span></td>
<!-- Above the table: "A circle means in stock, a square means back-ordered." -->How this gets tested
The W3C publishes test rules that define what a checker looks for here.
- Content has alternative for visual referenceA tool finds candidates, you decide
The other techniques filed under this rule
3 guides on this site are filed under 1.3.3 Sensory Characteristics. W3C documents this one as a failure of that rule, so it describes a way the rule gets broken rather than a way to pass it.
This guide is our interpretation of W3C technique F26: Failure of Success Criterion 1.3.3 due to using a graphical symbol alone to convey information. W3C publishes its techniques as guidance rather than as the standard, and says so on every one of them. The success criterion is what conformance is measured against, and a technique is one documented way to meet it.