`Header` is a "sister" class of `Path`, `Query` and `Cookie`. It also inherits from the same common `Param` class.

But remember that when you import `Query`, `Path`, `Header`, and others from `fastapi`, those are actually functions that return special classes.

///

/// info

To declare headers, you need to use `Header`, because otherwise the parameters would be interpreted as query parameters.

///

## Automatic conversion { #automatic-conversion }

You can see the required headers in the docs UI at `/docs`:

<div class="screenshot">
<img src="/img/tutorial/header-param-models/image01.png">
</div>

## Forbid Extra Headers { #forbid-extra-headers }

In some special use cases (probably not very common), you might want to **restrict** the headers that you want to receive.

You can use Pydantic's model configuration to `forbid` any `extra` fields:

   * @since 8.0
   */
  public static final byte DLE = 16;

  /**
   * Device Control 1. Characters for the control of ancillary devices associated with data
   * processing or telecommunication systems, more especially switching devices "on" or "off." (If a
   * single "stop" control is required to interrupt or turn off ancillary devices, DC4 is the
   * preferred assignment.)
   *
   * @since 8.0
   */

        assertNull(result1);
        assertNull(result2);
    }

    @Test
    void testGetSecurityWithSpecialCharactersInSecurityDescriptor() throws Exception {
        // Test with security descriptor containing special byte values but invalid structure
        srvsvc.ShareInfo502 info502 = new srvsvc.ShareInfo502();
        byte[] specialBytes = new byte[] { 0, -1, 127, -128, 64 };
        info502.security_descriptor = specialBytes;

        assertEquals(message, exception.getMessage());
        assertNull(exception.getCause());
    }

    public void test_constructor_withSpecialCharacters() {
        // Test with special characters in message
        String message = "Search not supported: \n\t!@#$%^&*(){}[]|\\:;\"'<>,.?/~`";
        UnsupportedSearchException exception = new UnsupportedSearchException(message);

 * the proxy. This proxy connection is called a "TLS Tunnel" and is specified by
 * [RFC 2817][1]. The HTTP CONNECT request that creates this tunnel connection is special: it
 * does not participate in any [interceptors][Interceptor] or [event listeners][EventListener]. It
 * doesn't include the motivating request's HTTP headers or even its full URL; only the target

    private final int d;

    // Four 64-bit words of internal state.
    // The initial state corresponds to the ASCII string "somepseudorandomlygeneratedbytes",
    // big-endian encoded. There is nothing special about this value; the only requirement
    // was some asymmetry so that the initial v0 and v1 differ from v2 and v3.
    private long v0 = 0x736f6d6570736575L;
    private long v1 = 0x646f72616e646f6dL;

         * performed properly. The effect is that the code at index 1 is never found
         * (NT_STATUS_UNSUCCESSFUL). So here we factor out NT_STATUS_SUCCESS
         * as a special case (which it is).
         */
        if (errcode == 0) {
            return "NT_STATUS_SUCCESS";
        }
        if ((errcode & 0xC0000000) == 0xC0000000) {

`Cookie` es una clase "hermana" de `Path` y `Query`. También hereda de la misma clase común `Param`.

Pero recuerda que cuando importas `Query`, `Path`, `Cookie` y otros desde `fastapi`, en realidad son funciones que devuelven clases especiales.

///

/// info | Información

Para declarar cookies, necesitas usar `Cookie`, porque de lo contrario los parámetros serían interpretados como parámetros de query.

///

## Resumen

/**
 * Tests for the HttpHeaders class.
 *
 * @author Kurt Alfred Kluever
 */
@NullUnmarked
public class HttpHeadersTest extends TestCase {

  public void testConstantNameMatchesString() throws Exception {
    // Special case some of the weird HTTP Header names...
    ImmutableBiMap<String, String> specialCases =
        ImmutableBiMap.<String, String>builder()
            .put("CDN_LOOP", "CDN-Loop")
            .put("ETAG", "ETag")