XMLHttpRequest: getResponseHeader() method

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨July 2015⁩.

Note: This feature is available inWeb Workers, except forService Workers.

TheXMLHttpRequest methodgetResponseHeader() returns the string containing thetext of a particular header's value.

If there are multiple response headerswith the same name, then their values are returned as a single concatenated string,where each value is separated from the previous one by a pair of comma and space. ThegetResponseHeader() method returns the value as a UTF byte sequence.

Note:The search for the header name is case-insensitive.

If you need to get the raw string of all of the headers, use thegetAllResponseHeaders() method,which returns the entire raw header string.

Syntax

getResponseHeader(headerName)

Parameters

headerName: A string indicating the name of the header you want to return thetext value of.

Return value

A string representing the header's text value, ornullif either the response has not yet been received or the header doesn't exist in theresponse.

Examples

In this example, a request is created and sent, and areadystatechangehandler is established to look for thereadyStateto indicate that the headers have been received; when that is the case,the value of theContent-Type header is fetched. If theContent-Type isn't the desired value, theXMLHttpRequest iscanceled by callingabort().

const client = new XMLHttpRequest();client.open("GET", "unicorns-are-awesome.txt", true);client.send();client.onreadystatechange = () => {  if (client.readyState === client.HEADERS_RECEIVED) {    const contentType = client.getResponseHeader("Content-Type");    if (contentType !== myExpectedType) {      client.abort();    }  }};