Document: domain property
=========================

**Deprecated:** This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

 The **`domain`** property of the `Document`
 interface gets/sets the domain portion of the origin of the current
 document, as used by the same-origin policy.

Value
-----

A string.

### Exceptions

`SecurityError` `DOMException`

Use of this feature was blocked by a Permissions Policy.

Examples
--------

### Getting the domain

 For code running at the URL `https://developer.mozilla.org/en-US/docs/Web`,
 this example would set `currentDomain` to the string
 "`developer.mozilla.org`".


```js
const currentDomain = document.domain;
```


 The getter for this property returns the domain portion of the current document's
 origin. In most cases, this will be the hostname portion of the document's URL. However,
 there are some exceptions:

* If the page has an opaque origin, e.g. for a page with a data URL, then it will
 return the empty string.
* If the `document.domain` setter has been used, then
 it will return the value that was set.

 Although the getter is not dangerous in the same way that the setter is, it is likely
 simpler and more useful to use the `Location.hostname` property instead.
 Then you can avoid `document.domain` entirely:


```js
const currentHostname = location.hostname;
```


 For the URL `https://developer.mozilla.org/en-US/docs/Web`,
 `currentHostname` is also the string "`developer.mozilla.org`".
 Other alternatives that provide slightly different information are
 `Location.host`, which includes the port, and
 `origin`, which provides the full origin.

### Setting the domain


```js
document.domain = domainString;
```


 The setter for this property can be used to *change* a page's
 origin, and thus modify how certain security checks are performed. It
 can only be set to the same or a parent domain. For example, if
 `https://a.example.com` and `https://b.example.com` both use


```js
document.domain = "example.com";
```


 then they have both modified their origin to have the same domain, and they can now
 access each other's DOM directly—despite being cross-origin, which would normally
 prevent such access.

 Note that setting `document.domain` to its current value is not a no-op. It
 still changes the origin. For example, if one page sets


```js
document.domain = document.domain;
```


 then it will be counted as cross-origin from any other normally-same-origin pages that
 have not done the same thing.

#### Deprecation

 The `document.domain` setter is deprecated. It undermines the security
 protections provided by the same origin policy, and complicates the origin model in browsers, leading to
 interoperability problems and security bugs.

 Attempting to set `document.domain` is dangerous. It opens up full access to
 a page's DOM from *all* subdomains, which is likely not what is intended. It
 also removes the port component from the origin, so now your page can be accessed by
 other pages with the same IP address or same host component, even on a different port.

 This is especially insecure on shared hosting. For example, another shared hosting
 customer is able to host a site at the same IP address but on a different port, then
 setting `document.domain` will remove the same-origin protection that
 normally protects you from that other customer's site accessing your site's data.

 Similar problems occur with shared hosting sites that give each customer a different
 subdomain. If a site sets `document.domain`, any other customer on a
 different subdomain can now do the same thing, and start accessing the data of the
 original site.

 Instead of using `document.domain` to facilitate cross-origin communication,
 you should use `Window.postMessage` to send an asynchronous message to the
 other origin. This controlled access via message-passing is much more secure than the
 blanket exposure of all data caused by `document.domain`.

#### Failures

 The setter will throw a "`SecurityError`" `DOMException` in
 several cases:

* The `document-domain`
`Permissions-Policy` is disabled.
* The document is inside a sandboxed `<iframe>`.
* The document has no browsing context.
* The document's effective domain is `null`.
* The given value is neither the same as the page's current hostname, nor a parent
 domain of it.

 As an example of this last failure case, trying to set `document.domain` to
 `"example.org"` when on `https://example.com/` will throw.

 Additionally, as part of its deprecation, it will do nothing when combined with certain
 modern isolation features:

* If used on a cross-origin isolated page, i.e. one that uses the appropriate values
 for the `Cross-Origin-Opener-Policy` and
 `Cross-Origin-Embedder-Policy` HTTP headers
* If used on an origin-isolated page, i.e. one that uses the
 `Origin-Isolation` HTTP header

 Finally, setting `document.domain` does not change the origin used for
 origin-checks by some Web APIs, preventing sub-domain access via this mechanism.
 Affected APIs include (but are not limited to):
 `Window.localStorage`, `IndexedDB_API`, `BroadcastChannel`, `SharedWorker` .

Specifications
--------------

| Specification |
| --- |
| HTML Standard # relaxing-the-same-origin-restriction |

Browser compatibility
---------------------

BCD tables only load in the browser with JavaScript enabled. Enable JavaScript to view data.

See also
--------

* Same-origin policy
* `Location.hostname`
* `Location.host`
* `origin`