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If a CSS triangle vanished after a stylesheet change, a selector using the attribute substring operator *= may be matching more than intended. It matches when text appears anywhere in an attribute value—not only when it is a complete class name. That can make a rule relevant to an element with a longer class name, though the cascade still decides which declarations take effect.
What does [class*="..."] match?
In an attribute selector, *= means “contains this substring somewhere.” It operates on the full attribute value; it does not treat the value of class as a list of class tokens. MDN Web Docs describes [attr*=value] as matching an attribute value that “contains at least one occurrence of value within the string.” See MDN’s attribute selector reference.
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For example, [class*="triangle"] matches <div class="icon-triangle-alert">, because the characters triangle occur within the class attribute. By contrast, [class~="triangle"] looks for triangle as a complete whitespace-separated class token, so it does not match that example. This illustrates the operators’ behavior; it does not establish the exact selector or markup involved in any particular disappearance.
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Substring matching is not inherently wrong. It is appropriate when the intended condition is that an attribute contain a particular string. It is a poor substitute for class-token membership when the selector should match only a class named triangle.
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Which attribute selector expresses the intended match?
Choose the operator according to the structure of the attribute and the relationship you want to test. These operators are not interchangeable:
| Operator | What it matches | Example intent |
|---|---|---|
= |
An exact attribute value | The whole value is triangle |
~= |
A whitespace-separated token | The class list contains the complete token triangle |
|= |
An exact value or that value followed by a hyphen | A language-like value such as en or en-US |
^= |
A value beginning with the supplied text | An attribute value has a particular prefix |
$= |
A value ending with the supplied text | An attribute value has a particular suffix |
*= |
A value containing the supplied text anywhere | An attribute value includes a substring |
For class membership, use a class selector such as .triangle or the token form [class~="triangle"], depending on the code’s conventions. Use [class="triangle"] only when the entire class attribute must equal that single value; it will not match an element whose class attribute contains additional classes.
Attribute string matching is generally case-sensitive for non-enumerated HTML attributes such as class. CSS also provides an i modifier for ASCII case-insensitive matching when that behavior is appropriate, for example [data-state="open" i].
How to find why the triangle disappeared
- Inspect the live element. Open the browser’s DevTools, select the element where the triangle should appear, and read its current class and other relevant attributes. The live DOM can differ from the original HTML if scripts have modified it.
- Check matched rules and affected properties. In the Styles or Rules panel, identify which selectors match and which declarations are active or crossed out. Check the properties the triangle actually depends on. Its implementation might use borders, dimensions, a pseudo-element, or another technique; the symptom alone does not identify it.
- Search for broad attribute selectors. Look through the relevant stylesheets for selectors such as
[class*=...]or substring matches ondata-*attributes. Compare each operator with the intended relationship: exact value, token, prefix, suffix, or substring. - Trace the cascade for each property. A selector match makes its rule relevant, but does not prove its declaration wins. In DevTools, find the computed value and the rule supplying it.
- Make the narrowest correction and verify it. Change the selector to express the intended condition, then check that the triangle returns and that unrelated elements no longer match.
MDN’s Debugging CSS guide recommends using DevTools to investigate overridden styles. Its general observation that a more specific selector often overrides a change is a useful possibility to check—not evidence that specificity caused this particular failure.
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Why a matching selector may not hide the triangle
CSS first determines which rules are relevant, then resolves competing declarations through the cascade. Origin and importance are considered before specificity; specificity then helps distinguish applicable declarations. If declarations remain tied, further criteria such as scoping proximity and order of appearance can matter. MDN explains the sequence in its CSS cascade reference.
Class selectors and attribute selectors both contribute to the CLASS column of specificity. But the fact that a substring selector matches does not, by itself, establish that it overrode the triangle’s styling. The declarations, cascade context, importance, scope, and ordering all matter. Inspect the winning value before changing specificity or adding !important.
What the selector explanation does—and does not—establish
The reported cause is that one selector matched by substring. The selector semantics explain how that can happen: *= can match within a longer attribute value. Without the actual HTML and CSS, however, the precise selector, triangle implementation, affected property, competing declaration, and best fix cannot be identified. Treat a substring selector as a lead to verify in the live element and matched rules, not as proof of which declaration made the triangle disappear.
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