---
title: Error Responses
description: Default server responses for invalid requests and responses, and how errors reach your framework.
---

Server adapters reject invalid requests before the handler runs and check
handler output before it is sent. This page lists the default responses. Each
[server adapter](/docs/server/express#error-handling) documents how to replace
them.

## Default Responses

| Situation                                                                                  | Status | Body                            |
| ------------------------------------------------------------------------------------------ | ------ | ------------------------------- |
| Request `Content-Type` is not declared by the route                                        | `415`  | `{ message }`                   |
| Request body cannot be decoded by a built-in codec                                         | `400`  | `{ message }`                   |
| Request body exceeds `requestBodyLimit`                                                    | `413`  | `{ message }`                   |
| [Request validation](/docs/http-behavior/schemas#request-validation) fails                 | `400`  | `{ message, validationErrors }` |
| [Response validation](/docs/http-behavior/schemas#response-validation-on-the-server) fails | `500`  | `{ message }`                   |

Body decoding and `requestBodyLimit` only apply to adapters that decode request
bodies themselves. Adapters that use the framework's body parsing report those
failures through the framework.

The request validation body groups Standard Schema issues by location:

```ts
{
	message: string;
	validationErrors: {
		body: ValidationIssue[];
		query: ValidationIssue[];
		params: ValidationIssue[];
		headers: ValidationIssue[];
	};
}
```

The response validation body does not expose validation details.

## Validation Errors

Validation failures are represented by error classes exported from every server
adapter. Adapter error handlers receive them.

`RequestValidationError` has:

- `status`: the default status, `400`.
- `issues`: Standard Schema issues grouped by `body`, `query`, `params`, and `headers`.
- `responseBody`: the default response body.

`ResponseValidationError` has:

- `status`: the default status, `500`.
- `location`: `"body"`, `"headers"`, or `"stream"`.
- `issues`: the Standard Schema issues.
- `responseBody`: the default response body.

A stream item that fails validation after the stream has started cannot change
the response status. The stream ends instead.

## Other Errors

Errors thrown by handlers, middleware, or custom codecs are not converted into
responses. They propagate to the framework's error handling, or reject the
handler promise for the Fetch and Node adapters. Returning a status that the
route does not declare also produces an error.