Formik

Formik is an open-source library for building forms in React applications. It provides a set of components and hooks designed to manage form state, validation, and submission with reduced boilerplate. The library aims to simplify common form tasks such as tracking input values, handling changes and blur events, validating data, and managing submission status.

The core API centers on the Formik component and the useFormik hook, which expose form state such as values, errors, touched, and submission status. Inputs can be wired through the Field and ErrorMessage components, or by using the hook to connect custom inputs. Formik supports specifying initialValues, a validation schema or function, and an onSubmit handler. It handles change and blur events, provides helpers for resetting the form, and exposes indicators like isSubmitting and isValid to drive UI logic.

Validation in Formik can be performed with built-in validators or with external libraries, most commonly Yup, though any validator can be used. Validation can be configured to run on change, blur, or submission, allowing developers to tailor the user experience. Formik also supports nested values and arrays, which helps in building complex forms.

In practice, Formik is one of the most widely adopted form-management solutions in the React ecosystem. It emphasizes a predictable, declarative approach to form data and side effects, and a large ecosystem of tutorials and community examples supports its use. It is typically compared with other form libraries that prioritize different trade-offs, such as performance or API ergonomics.