# Attributes and attribute values

Attributes make choices such as color, size, and material consistent across a catalog.
They are useful when buyers select an option or filter products by a structured value.

## Definitions, assignments, and selections

An attribute defines a dimension.
Its attribute values define the allowed choices.
A product assignment determines which choices apply to that product.
A variant selects values from those assignments.

For a shirt in two colors and three sizes, the product can have Color and Size assignments.
Create a variant for each combination you actually sell.
A storefront must not offer every theoretical combination unless a returned variant represents it.

## Choose attributes for choices

Use attributes for reusable options and discovery.
Use [categories](/concepts/catalog/categories) for navigation, [collections](/concepts/catalog/collections) for curated groups, and [metafields](/concepts/custom-data/metafields) for typed data such as a care instruction or technical specification.
A tag is useful for a lightweight label that does not need an option definition.

## Changing an option safely

Create definitions and allowed values before assigning them to products and variants.
Preserve IDs when changing display names.
Before removing a value, check the products and variants that use it and update their selections deliberately.
Reordering options should change their presentation, not their identity.

To expose an attribute as a filter, [configure a facet](/guides/storefront/facets).
Use its returned `queryField` in the storefront instead of deriving a search field from the attribute's display name.

See [attributeCreate](/api/admin-graphql/mutations/attribute-create) and [AttributeAssignmentInput](/api/admin-graphql/inputs/attribute-assignment-input) for the exact contracts.