Permissions-Policy: loopback-network directive
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The HTTP Permissions-Policy header loopback-network directive controls whether the current document is allowed to make network requests to loopback addresses.
A loopback address is only accessible on the local host; its target will differ on every device. For example, 127.0.0.1, which is generally known as localhost.
Specifically, where a defined policy blocks use of this feature, requests to loopback addresses will always fail.
See Local Network Access for more details.
Syntax
Permissions-Policy: loopback-network=<allowlist>;
<allowlist>-
A list of origins for which permission is granted to use the feature. See
Permissions-Policy> Syntax for more details.
Default policy
The default allowlist for loopback-network is self. The top-level browsing context and same-origin iframes are allowed access to the loopback-network feature by default.
Examples
Basic usage
SecureCorp Inc. wants to disallow loopback-network within all cross-origin iframes except those whose origin is https://example.com. It can do so by delivering the following HTTP response header to define a Permissions Policy:
Permissions-Policy: loopback-network=(self "https://example.com")
SecureCorp Inc. must also include an allow attribute on each <iframe> element where loopback-network is to be allowed:
<iframe src="https://example.com/lna" allow="loopback-network"></iframe>
Note:
Specifying the Permissions-Policy header in this manner disallows loopback-network for other origins, even if they are allowed by the <iframe> allow attribute.
Using the default policy
If an allowlist for loopback-network is not defined by a Permissions-Policy response header, user agents will apply the default allowlist self. In this mode, loopback-network is automatically allowed in the top-level browsing context and same-origin iframes, but not in cross-origin iframes.
To allow loopback-network in a cross-origin iframe, include an allow attribute on the <iframe> element:
<iframe src="https://other.com/lna" allow="loopback-network"></iframe>
Specifications
| Specification |
|---|
| Local Network Access # permissiondef-loopback-network |