# 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`.

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)

# 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`. 🤓

///

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 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

		clientKey, err = crypto.SSEC.ParseHTTP(header)
		if err != nil {
			return
		}
		if sse, err = encrypt.NewSSEC(clientKey[:]); err != nil {
			return
		}
		opts.ServerSideEncryption = sse
		return
	}
	if crypto.S3.IsRequested(header) || (metadata != nil && crypto.S3.IsEncrypted(metadata)) {
		opts.ServerSideEncryption = encrypt.NewSSE()
	}

	return
}

// get ObjectOptions for GET calls from encryption headers

When writing request headers, use `header(name, value)` to set the only occurrence of `name` to `value`. If there are existing values, they will be removed before the new value is added. Use `addHeader(name, value)` to add a header without removing the headers already present.

		if crypto.S3.IsEncrypted(info.UserDefined) && r.Header.Get(xhttp.AmzCopySource) == "" {
			if crypto.SSEC.IsRequested(headers) || crypto.SSECopy.IsRequested(headers) {
				return encrypted, errEncryptedObject
			}
		}

		if crypto.S3KMS.IsEncrypted(info.UserDefined) && r.Header.Get(xhttp.AmzCopySource) == "" {
			if crypto.SSEC.IsRequested(headers) || crypto.SSECopy.IsRequested(headers) {
				return encrypted, errEncryptedObject

}

// Return canonical headers.
func canonicalizedAmzHeadersV2(headers http.Header) string {
	var keys []string
	keyval := make(map[string]string, len(headers))
	for key := range headers {
		lkey := strings.ToLower(key)
		if !strings.HasPrefix(lkey, "x-amz-") {
			continue
		}
		keys = append(keys, lkey)
		keyval[lkey] = strings.Join(headers[key], ",")
	}
	sort.Strings(keys)

          response.request
            .newBuilder()
            .header("Authorization", "XYZ")
            .build()
        }.build()
    server.enqueue(
      MockResponse(
        code = 401,
        body = "{\"error\":{\"message\":\"No auth credentials found\",\"code\":401}}",
        headers = Headers.headersOf("content-type", "application/json"),
      ),
    )
    server.enqueue(