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Case Insensitive CSS Attribute Selector

David Walsh
Published: June 19, 2024

CSS selectors never cease to amaze me in how powerful they can be in matching complex patterns. Most of that flexibility is in parent/child/sibling relationships, very seldomly in value matching. Consider my surprise when I learned that CSS allows matching attribute values regardless off case!

Adding a {space}i to the attribute selector brackets will make the attribute value search case insensitive:

/* case sensitive, only matches "example" */
[class=example] {
  background: pink;
/* case insensitive, matches "example", "eXampLe", etc. */
[class=example i] {
  background: lightblue;

The use cases for this i flag are likely very limited, especially if this flag is knew knowledge for you and you’re used to a standard lower-case standard. A loose CSS classname standard will have and would continue to lead to problems, so use this case insensitivity flag sparingly!

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