open fun url(url: URL) = url(url.toString().toHttpUrl())

    /**
     * Sets the header named [name] to [value]. If this request already has any headers
     * with that name, they are all replaced.
     */
    open fun header(
      name: String,
      value: String,
    ) = commonHeader(name, value)

    /**
     * Adds a header with [name] and [value]. Prefer this method for multiply-valued
     * headers like "Cookie".

        // If there's a "Expect: 100-continue" header on the request, wait for a "HTTP/1.1 100
        // Continue" response before transmitting the request body. If we don't get that, return
        // what we did get (such as a 4xx response) without ever transmitting the request body.
        if ("100-continue".equals(request.header("Expect"), ignoreCase = true)) {
          exchange.flushRequest()

      builder.header("", "Value")
    }
    assertFailsWith<IllegalArgumentException> {
      builder.addHeader("", "Value")
    }
  }

  @Test
  fun headerAllowsTabOnlyInValues() {
    val builder = Request.Builder()
    builder.header("key", "sample\tvalue")
    assertFailsWith<IllegalArgumentException> {
      builder.header("sample\tkey", "value")
    }
  }

that are absent from the original request, including `Content-Length`, `Transfer-Encoding`, `User-Agent`, `Host`, `Connection`, and `Content-Type`. It will add an `Accept-Encoding` header for transparent response compression unless the header is already present. If you’ve got cookies, OkHttp will add a `Cookie` header with them.

Some requests will have a cached response. When this cached response isn’t fresh, OkHttp can do a _conditional GET_ to download an updated response if it’s newer...

      ProtocolException::class.java,
      "Expected 'Sec-WebSocket-Accept' header value 'ujmZX4KXZqjwy6vi1aQFH5p4Ygk=' but was 'magic'",
    )
    webSocket.cancel()
  }

  @Test
  @Throws(IOException::class)
  fun clientIncludesForbiddenHeader() {
    newWebSocket(
      Request.Builder()
        .url(webServer.url("/"))
        .header("Sec-WebSocket-Extensions", "permessage-deflate")
        .build(),
    )

# HTTP Basic Auth

For the simplest cases, you can use HTTP Basic Auth.

In HTTP Basic Auth, the application expects a header that contains a username and a password.

If it doesn't receive it, it returns an HTTP 401 "Unauthorized" error.

And returns a header `WWW-Authenticate` with a value of `Basic`, and an optional `realm` parameter.

That tells the browser to show the integrated prompt for a username and password.

* `headers` - A `dict` of strings.
* `media_type` - A `str` giving the media type. E.g. `"text/html"`.

FastAPI (actually Starlette) will automatically include a Content-Length header. It will also include a Content-Type header, based on the media_type and appending a charset for text types.

```Python hl_lines="1  18"
{!../../../docs_src/response_directly/tutorial002.py!}
```

### `HTMLResponse`

  return millis.toInt()
}

internal fun List<Header>.toHeaders(): Headers {
  val builder = Headers.Builder()
  for ((name, value) in this) {
    builder.addLenient(name.utf8(), value.utf8())
  }
  return builder.build()
}

internal fun Headers.toHeaderList(): List<Header> =
  (0 until size).map {
    Header(name(it), value(it))
  }

            .build()

        networkResponse.body.close()

        // Update the cache after combining headers but before stripping the
        // Content-Encoding header (as performed by initContentStream()).
        cache!!.trackConditionalCacheHit()
        cache.update(cacheResponse, response)
        return response.also {
          listener.cacheHit(call, it)
        }

If the argument to [FileInfoHeader] implements the new [FileInfoNames]
interface, then the interface methods will be used to set the Uname/Gname
of the file header. This allows applications to override the system-dependent