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.
For code running at the URL
this example would set
currentDomain to the string
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.
document.domainsetter 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
const currentHostname = location.hostname;
For the URL
currentHostname is also the string "
Other alternatives that provide slightly different information are
Location.host, which includes the port, and
origin, which provides the full origin.
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://b.example.com both use
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
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.
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
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
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
The setter will throw a "
- The document is inside a sandboxed
- The document has no browsing context.
- The document's effective domain is
- 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
"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
If used on an origin-isolated page, i.e. one that uses the
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):
BCD tables only load in the browser