The Headers interface of the Fetch API allows you to perform various actions on HTTP request and response headers. These actions include retrieving, setting, adding to, and removing. A Headers object has an associated header list, which is initially empty and consists of zero or more name and value pairs.  You can add to this using methods like append() (see Examples.) In all methods of this interface, header names are matched by case-insensitive byte sequence. 

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.

A Headers object also has an associated guard, which takes a value of immutable, request, request-no-cors, response, or none. This affects whether the set(), delete(), and append() methods will mutate the header. For more information see Guard.

You can retrieve a Headers object via the Request.headers and Response.headers properties, and create a new Headers object using the Headers.Headers() constructor.

An object implementing Headers can directly be used in a for...of structure, instead of entries(): for (var p of myHeaders) is equivalent to for (var p of myHeaders.entries()).

Note: you can find more out about the available headers by reading our HTTP headers reference.

Constructor

Headers.Headers()
Creates a new Headers object.

Methods

Headers.append()
Appends a new value onto an existing header inside a Headers object, or adds the header if it does not already exist.
Headers.delete()
Deletes a header from a Headers object.
Headers.entries()
Returns an iterator allowing to go through all key/value pairs contained in this object.
Headers.forEach()
Executes a provided function once for each array element.
Headers.get()
Returns a ByteString sequence of all the values of a header within a Headers object with a given name.
Headers.has()
Returns a boolean stating whether a Headers object contains a certain header.
Headers.keys()
Returns an iterator allowing you to go through all keys of the key/value pairs contained in this object.
Headers.set()
Sets a new value for an existing header inside a Headers object, or adds the header if it does not already exist.
Headers.values()
Returns an iterator allowing you to go through all values of the key/value pairs contained in this object.

Note: To be clear, the difference between Headers.set() and Headers.append() is that if the specified header does already exist and does accept multiple values, Headers.set() will overwrite the existing value with the new one, whereas Headers.append() will append the new value onto the end of the set of values. See their dedicated pages for example code.

Note: All of the Headers methods will throw a TypeError if you try to pass in a reference to a name that isn't a valid HTTP Header name. The mutation operations will throw a TypeError if the header has an immutable Guard. In any other failure case they fail silently.

Note: When Header values are iterated over, they are automatically sorted in lexicographical order, and values from duplicate header names are combined.

Obsolete methods

Headers.getAll()
Used to return an array of all the values of a header within a Headers object with a given name; this method has now been deleted from the spec, and Headers.get() now returns all values instead of just one.

Examples

In the following snippet, we create a new header using the Headers() constructor, add a new header to it using append(), then return that header value using get():

var myHeaders = new Headers();

myHeaders.append('Content-Type', 'text/xml');
myHeaders.get('Content-Type') // should return 'text/xml'

The same can be achieved by passing an array of arrays or an object literal to the constructor:

var myHeaders = new Headers({
    'Content-Type': 'text/xml'
});

// or, using an array of arrays:
myHeaders = new Headers([
    ['Content-Type', 'text/xml']
]);

myHeaders.get('Content-Type') // should return 'text/xml'

Specifications

Specification Status Comment
Fetch
The definition of 'Headers' in that specification.
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 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Full support YesFirefox Full support 39
Full support 39
Full support 34
Disabled
Disabled From version 34: this feature is behind the dom.fetch.enabled preference. To change preferences in Firefox, visit about:config.
IE No support NoOpera Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari Full support 10.1WebView Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference.
Chrome Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Mobile ? Firefox Android Full support 44Opera Android Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari iOS No support NoSamsung Internet Android Full support 4.0
Lexicographical sorting, and values from duplicate header names combined when iterated.Chrome ? Edge ? Firefox Full support 44IE No support NoOpera Full support 24Safari No support NoWebView Android ? Chrome Android ? Edge Mobile ? Firefox Android No support NoOpera Android ? Safari iOS No support NoSamsung Internet Android ?
Headers() constructor
Experimental
Chrome Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge ? Firefox Full support 39
Full support 39
Full support 34
Disabled
Disabled From version 34: this feature is behind the dom.fetch.enabled preference. To change preferences in Firefox, visit about:config.
IE No support NoOpera Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari Full support 10.1WebView Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference.
Chrome Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Mobile ? Firefox Android No support NoOpera Android Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the preference.
Safari iOS No support NoSamsung Internet Android Full support 4.0
append
Experimental
Chrome Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Full support YesFirefox Full support 39
Full support 39
Full support 34
Disabled
Disabled From version 34: this feature is behind the dom.fetch.enabled preference. To change preferences in Firefox, visit about:config.
IE No support NoOpera Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari Full support 10.1WebView Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference.
Chrome Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Mobile Full support YesFirefox Android No support NoOpera Android Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari iOS No support NoSamsung Internet Android Full support 4.0
delete
Experimental
Chrome Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Full support YesFirefox Full support 39
Full support 39
Full support 34
Disabled
Disabled From version 34: this feature is behind the dom.fetch.enabled preference. To change preferences in Firefox, visit about:config.
IE No support NoOpera Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari Full support 10.1WebView Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference.
Chrome Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Mobile Full support YesFirefox Android No support NoOpera Android Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari iOS No support NoSamsung Internet Android Full support 4.0
entries
Experimental
Chrome Full support 45Edge Full support 16Firefox Full support 44IE ? Opera Full support 32Safari ? WebView Android Full support 45Chrome Android Full support 45Edge Mobile Full support YesFirefox Android Full support 44Opera Android Full support 32Safari iOS ? Samsung Internet Android Full support 5.0
get
Experimental
Chrome Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Full support YesFirefox Full support 52
Notes
Full support 52
Notes
Notes Prior to Firefox 52, get() only returned the first value in the specified header, with getAll() returning all values. From 52 onwards, get() now returns all values and getAll() has been deleted.
Full support 39
Full support 34
Disabled
Disabled From version 34: this feature is behind the dom.fetch.enabled preference. To change preferences in Firefox, visit about:config.
IE No support NoOpera Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari Full support 10.1WebView Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference.
Chrome Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Mobile Full support YesFirefox Android No support NoOpera Android Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari iOS No support NoSamsung Internet Android Full support 4.0
getAll
ExperimentalDeprecatedNon-standard
Chrome No support 42 — 60Edge Full support YesFirefox No support 39 — 52
No support 39 — 52
Full support 34
Disabled
Disabled From version 34: this feature is behind the dom.fetch.enabled preference. To change preferences in Firefox, visit about:config.
IE No support NoOpera No support 29 — 47Safari No support NoWebView Android No support 42 — 60Chrome Android No support 42 — 60Edge Mobile Full support YesFirefox Android No support NoOpera Android No support 29 — 47Safari iOS No support NoSamsung Internet Android Full support 4.0
has
Experimental
Chrome Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Full support YesFirefox Full support 39
Full support 39
Full support 34
Disabled
Disabled From version 34: this feature is behind the dom.fetch.enabled preference. To change preferences in Firefox, visit about:config.
IE No support NoOpera Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari No support NoWebView Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference.
Chrome Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Mobile Full support YesFirefox Android No support NoOpera Android Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari iOS No support NoSamsung Internet Android Full support 4.0
keys
Experimental
Chrome Full support 45Edge Full support 16Firefox Full support 44IE ? Opera Full support 32Safari ? WebView Android Full support 45Chrome Android Full support 45Edge Mobile Full support YesFirefox Android Full support 44Opera Android Full support 32Safari iOS ? Samsung Internet Android Full support 5.0
set
Experimental
Chrome Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Full support YesFirefox Full support 39
Full support 39
Full support 34
Disabled
Disabled From version 34: this feature is behind the dom.fetch.enabled preference. To change preferences in Firefox, visit about:config.
IE No support NoOpera Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari No support NoWebView Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference.
Chrome Android Full support 42
Full support 42
Full support 41
Disabled
Disabled From version 41: this feature is behind the Experimental Web Platform Features preference. To change preferences in Chrome, visit chrome://flags.
Edge Mobile Full support YesFirefox Android No support NoOpera Android Full support 29
Full support 29
Full support 28
Disabled
Disabled From version 28: this feature is behind the Experimental Web Platform Features preference.
Safari iOS No support NoSamsung Internet Android Full support 4.0
values
Experimental
Chrome Full support 45Edge Full support 16Firefox Full support 44IE ? Opera Full support 32Safari ? WebView Android Full support 45Chrome Android Full support 45Edge Mobile Full support YesFirefox Android Full support 44Opera Android Full support 32Safari iOS ? Samsung Internet Android Full support 5.0

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
Non-standard. Expect poor cross-browser support.
Non-standard. Expect poor cross-browser support.
Deprecated. Not for use in new websites.
Deprecated. Not for use in new websites.
See implementation notes.
See implementation notes.
User must explicitly enable this feature.
User must explicitly enable this feature.

See also

 

Document Tags and Contributors

Last updated by: fscholz,