**FastAPI** will **extract** the data for **each field** from the **headers** in the request and give you the Pydantic model you defined.

## Check the Docs { #check-the-docs }

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 }

import okhttp3.internal.http2.Header
import okio.ByteString

/**
 * Representation of an individual case (set of headers and wire format). There are many cases for a
 * single story.  This class is used reflectively with Moshi to parse stories.
 */
data class Case(
  val seqno: Int = 0,
  val wire: ByteString? = null,
  val headers: List<Map<String, String>>,
) : Cloneable {
  val headersList: List<Header>
    get() {

    }

  fun assertHeader(
    name: String,
    vararg values: String?,
  ) = apply {
    assertThat(response!!.headers(name)).containsExactly(*values)
  }

  fun assertHeaders(headers: Headers) =
    apply {
      assertThat(response!!.headers).isEqualTo(headers)
    }

  fun assertBody(expectedBody: String) =
    apply {
      assertThat(body).isEqualTo(expectedBody)
    }

   readTimeoutMillis, retryOnConnectionFailure, socketFactory, sslSocketFactory, writeTimeoutMillis
 * **PushPromise**: headers, method, path, response
 * **Request**: body, cacheControl, headers, method, url
 * **Response**: body, cacheControl, cacheResponse, code, handshake, headers, message,
   networkResponse, priorResponse, protocol, receivedResponseAtMillis, request, sentRequestAtMillis

    val recorded = server.takeRequest()
    assertThat(recorded.headers["Accept"]).isEqualTo("text/plain")
    assertThat(recorded.headers["Accept-Encoding"]).isEqualTo("gzip")
    assertThat(recorded.headers["Connection"]).isNull()
    assertThat(recorded.headers["User-Agent"]!!).matches(Regex("Jetty/.*"))
  }

## Proxy Forwarded Headers { #proxy-forwarded-headers }

When using a proxy to handle HTTPS, your **application server** (for example Uvicorn via FastAPI CLI) doesn't known anything about the HTTPS process, it communicates with plain HTTP with the **TLS Termination Proxy**.

      .build()
  }

  companion object {
    /** Combines cached headers with a network headers as defined by RFC 7234, 4.3.4. */
    private fun combine(
      cachedHeaders: Headers,
      networkHeaders: Headers,
    ): Headers {
      val result = Headers.Builder()

      for (index in 0 until cachedHeaders.size) {
        val fieldName = cachedHeaders.name(index)

        headers = Headers.headersOf("content-type", "application/json"),
      ),
    )
    server.enqueue(
      MockResponse(
        body =
          """
          |data: hey
          |
          |
          """.trimMargin(),
        headers = Headers.headersOf("content-type", "text/event-stream"),
      ),
    )

        }
      }

      // There's another part. Parse its headers and return it.
      val headers = HeadersReader(source).readHeaders()
      val partSource = PartSource()
      currentPart = partSource
      return Part(headers, partSource.buffer())
    }

    /** A single part in the stream. It is an error to read this after calling [nextPart]. */

	public final fun getThrottleBytesPerPeriod ()J
	public final fun getThrottlePeriodNanos ()J
	public final fun getTrailers ()Lokhttp3/Headers;
	public final fun getTrailersDelayNanos ()J
	public final fun getWebSocketListener ()Lokhttp3/WebSocketListener;
	public final fun headers (Lokhttp3/Headers;)Lmockwebserver3/MockResponse$Builder;
	public final fun headersDelay (JLjava/util/concurrent/TimeUnit;)Lmockwebserver3/MockResponse$Builder;