# Validation

> Making sure everything's right in the world


When receiving incoming requests it's best practice to validate the
payload to make sure it meets your expectations, contains all the necessary
fields, and so on.

Encore provides an out-of-the-box middleware that automatically validates
incoming requests if the request type implements the method `Validate() error`.

If it does, Encore will call this method after deserializing the request payload,
and only call your API handler (and other middleware) if the validation function
returns `nil`.

If the validation function returns an [`*errs.Error`](/docs/go/primitives/api-errors) that error
is reported unmodified to the caller. Other errors are converted to an `*errs.Error`
with code `InvalidArgument`, which results in a HTTP response with status code `400 Bad Request`.

This design means that it's easy to use your validation library of choice.
In the future we're looking to provide an out-of-the-box validation library
for an even better developer experience.