CSP: fenced-frame-src

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The HTTP Content-Security-Policy (CSP) fenced-frame-src directive specifies valid sources for nested browsing contexts loaded into <fencedframe> elements.

CSP version 1
Directive type Fetch directive
Fallback If this directive is absent, the user agent will look for the frame-src directive (which falls back to the child-src directive).


One or more sources can be allowed for the fenced-frame-src policy:

Content-Security-Policy: fenced-frame-src <source>;
Content-Security-Policy: fenced-frame-src <source> <source>;


<source>s for fenced-frame-src are more limited than for frame-src. Only the following source expressions can be used:

  • The scheme-source "https:"
  • The host-source "https://*:*"
  • The string "*"

Note: See the full list of CSP Source Values.


Violation cases

Given this CSP header:

Content-Security-Policy: fenced-frame-src https://example.com/

The following sources will not load in a fenced frame:

  • https://not-example.com/ (domain doesn't match)
  • https://example.org/ (TLD doesn't match)


Fenced Frame
# new-csp-directive

Browser compatibility

BCD tables only load in the browser

See also