# Header Parameters { #header-parameters }

You can define Header parameters the same way you define `Query`, `Path` and `Cookie` parameters.

## Import `Header` { #import-header }

First import `Header`:

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[3] *}

## Declare `Header` parameters { #declare-header-parameters }

Then declare the header parameters using the same structure as with `Path`, `Query` and `Cookie`.

# Header Parameter Models { #header-parameter-models }

If you have a group of related **header parameters**, you can create a **Pydantic model** to declare them.

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

func setEventStreamHeaders(w http.ResponseWriter) {
	w.Header().Set(xhttp.ContentType, "text/event-stream")
	w.Header().Set(xhttp.CacheControl, "no-cache") // nginx to turn off buffering
	w.Header().Set("X-Accel-Buffering", "no")      // nginx to turn off buffering
}

// Write http common headers
func setCommonHeaders(w http.ResponseWriter) {
	// Set the "Server" http header.
	w.Header().Set(xhttp.ServerInfo, MinioStoreName)

	reader, err := sio.DecryptReader(client, sio.Config{
		Key:            objectEncryptionKey,
		SequenceNumber: seqNumber,
	})
	if err != nil {
		return nil, crypto.ErrInvalidCustomerKey
	}
	return reader, nil
}

// DecryptBlocksRequestR - same as DecryptBlocksRequest but with a
// reader

And as the `Response` can be used frequently to set headers and cookies, **FastAPI** also provides it at `fastapi.Response`.

///

## Custom Headers { #custom-headers }

Keep in mind that custom proprietary headers can be added <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">using the 'X-' prefix</a>.

		return
	}

	const mapEntryOverhead = 200

	var (
		reader        io.Reader
		actualSize    int64 = -1
		fileName      string
		fanOutEntries = make([]minio.PutObjectFanOutEntry, 0, 100)
	)

	maxParts := 1000
	// Canonicalize the form values into http.Header.
	formValues := make(http.Header)
	var headerLen int64
	for {
		part, err := mp.NextRawPart()

    internal val reader: Http2Reader,
  ) : Http2Reader.Handler,
    () -> Unit {
    override fun invoke() {
      var connectionErrorCode = ErrorCode.INTERNAL_ERROR
      var streamErrorCode = ErrorCode.INTERNAL_ERROR
      var errorException: IOException? = null
      try {
        reader.readConnectionPreface(this)
        while (reader.nextFrame(false, this)) {
        }

        .protocols(ONLY_HTTP1)
        .build()
    val request =
      originalRequest
        .newBuilder()
        .header("Upgrade", "websocket")
        .header("Connection", "Upgrade")
        .header("Sec-WebSocket-Key", key)
        .header("Sec-WebSocket-Version", "13")
        .header("Sec-WebSocket-Extensions", "permessage-deflate")
        .build()
    call = RealCall(webSocketClient, request, forWebSocket = true)

		return map[string]string{}
	}
	return map[string]string{
		"requestId":      w.Header().Get(xhttp.AmzRequestID),
		"nodeId":         w.Header().Get(xhttp.AmzRequestHostID),
		"content-length": w.Header().Get(xhttp.ContentLength),
		// Add more fields here.
	}
}

// Trims away `aws-chunked` from the content-encoding header if present.
// Streaming signature clients can have custom content-encoding such as

	UserTags string

	// List of individual parts, maximum size of upto 10,000
	Parts []ObjectPartInfo `json:"-"`

	// Implements writer and reader used by CopyObject API
	Writer       io.WriteCloser `json:"-" msg:"-"`
	Reader       *hash.Reader   `json:"-" msg:"-"`
	PutObjReader *PutObjReader  `json:"-" msg:"-"`

	metadataOnly bool
	versionOnly  bool // adds a new version, only used by CopyObject