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CSP: frame-ancestors

The HTTP Content-Security-Policy (CSP) frame-ancestors directive specifies valid parents that may embed a page using <frame>, <iframe>, <object>, <embed>, or <applet>.

Setting this directive to 'none' is similar to X-Frame-Options: DENY (which is also supported in older browers).

CSP version 2
Directive type Navigation directive
default-src fallback No. Not setting this allows anything.
This directive is not supported in the <meta> element.

Syntax

One or more sources can be set for the frame-ancestors policy:

Content-Security-Policy: frame-ancestors <source>;
Content-Security-Policy: frame-ancestors <source> <source>;

Sources

<source> can be one of the following:

The frame-ancestors directive’s syntax is similar to a source list of other directives (e.g. default-src, but doesn't allow 'unsafe-eval' or 'unsafe-inline' for example. It will also not fall back to a default-src setting. Only the sources listed below are allowed:

<host-source>
Internet hosts by name or IP address, as well as an optional URL scheme and/or port number. The site's address may include an optional leading wildcard (the asterisk character, '*'), and you may use a wildcard (again, '*') as the port number, indicating that all legal ports are valid for the source.
Examples:
  • http://*.example.com: Matches all attempts to load from any subdomain of example.com using the http: URL scheme.
  • mail.example.com:443: Matches all attempts to access port 443 on mail.example.com.
  • https://store.example.com: Matches all attempts to access store.example.com using https:.
<scheme-source>
A schema such as 'http:' or 'https:'. The colon is required. You can also specify data schemas (not recommended).
  • 'data:' Allows data: URIs to be used as a content source. This is insecure; an attacker can also inject arbitrary data: URIs. Use this sparingly and definitely not for scripts.
  • 'mediastream:' Allows mediastream: URIs to be used as a content source.
  • 'blob:' Allows blob: URIs to be used as a content source.
  • 'filesystem:' Allows filesystem: URIs to be used as a content source.
'self'
Refers to the origin from which the protected document is being served, including the same URL scheme and port number. You must include the single quotes. Some browsers specifically exclude blob and filesystem from source directives. Sites needing to allow these content types can specify them using the Data attribute.
'none'
Refers to the empty set; that is, no URLs match. The single quotes are required.

Examples

Content-Security-Policy: frame-ancestors 'none';

Specifications

Specification Status Comment
Content Security Policy Level 3
The definition of 'frame-ancestors' in that specification.		 Editor's Draft No changes.
Content Security Policy Level 2
The definition of 'frame-ancestors' in that specification.		 Recommendation Initial definition.

Browser compatibility

Feature Chrome Edge Firefox Internet Explorer Opera Safari
Basic support 40 No 331 No 26 10
Feature Android webview Chrome for Android Edge mobile Firefox for Android IE mobile Opera Android iOS Safari
Basic support ? Yes No 332 No ? 9.3

1. Before Firefox 58, frame-ancestors is ignored in Content-Security-Policy-Report-Only.

2. Before Firefox for Android 58, frame-ancestors is ignored in Content-Security-Policy-Report-Only.

See also

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https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/frame-ancestors