The XMLHttpRequest method setRequestHeader() sets the value of an HTTP request header. When using setRequestHeader(), you must call it after calling open(), but before calling send(). If this method is called several times with the same header, the values are merged into one single request header.

Each time you call setRequestHeader() after the first time you call it, the specified text is appended to the end of the existing header's content.

If no Accept header has been set using this, an Accept header with the type "*/*" is sent with the request when send() is called.

For security reasons, some headers can only be controlled by the user agent. These headers include the forbidden header names  and forbidden response header names.

Note: For your custom fields, you may encounter a "not allowed by Access-Control-Allow-Headers in preflight response" exception when you send requests across domains. In this situation, you need to set up the Access-Control-Allow-Headers in your response header at server side.

Syntax

XMLHttpRequest.setRequestHeader(header, value)

Parameters

header
The name of the header whose value is to be set.
value
The value to set as the body of the header.

Return value

undefined.

Specifications

Specification Status Comment
XMLHttpRequest
The definition of 'setRequestHeader()' in that specification.
Living Standard WHATWG living standard

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic supportChrome Full support 1Edge Full support 12Firefox Full support YesIE Full support 7
Full support 7
Full support 5
Notes
Notes Implemented via ActiveXObject
Opera Full support YesSafari Full support 1.2WebView Android Full support YesChrome Android Full support 18Edge Mobile Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes

Legend

Full support  
Full support
See implementation notes.
See implementation notes.

See also

Document Tags and Contributors

Last updated by: Sheppy,