> For the complete documentation index, see [llms.txt](https://structure.js.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://structure.js.org/v1/coercion.md).

# Coercion

Structure does type coercion based on the declared [schema](/v1/schema-concept.md). It's important to note that it **never** coerces the following scenarios:

* `undefined`;
* `null` when `nullable` option is enabled;
* value is already of the declared type (except for arrays, we'll talk more about this soon).

Let's break the coercion into 3 categories.