Skip to content
Biome
Docs Playground
Blog

noDuplicateProperties

Diagnostic Category: lint/nursery/noDuplicateProperties

Since: v1.9.4

Sources:

Disallow duplicate properties within declaration blocks.

This rule checks the declaration blocks for duplicate properties. It ignores custom properties.

Examples

Section titled Examples

Invalid

Section titled Invalid
a {
  color: pink;
  color: orange;
}
code-block.css:3:3 lint/nursery/noDuplicateProperties ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Duplicate properties can lead to unexpected behavior and may override previous declarations unintentionally.
  
    1 │ a {
    2 │   color: pink;
  > 3 │   color: orange;
      │   ^^^^^
    4 │ }
    5 │ 
  
  ℹ color is already defined here.
  
    1 │ a {
  > 2 │   color: pink;
      │   ^^^^^
    3 │   color: orange;
    4 │ }
  
  ℹ Remove or rename the duplicate property to ensure consistent styling.

Valid

Section titled Valid
a {
  color: pink;
  background: orange;
}
Section titled Related links