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Type String
Mandatory No
"content_security_policy": "default-src 'self'"

Extensions have a content security policy applied to them by default. The default policy restricts the sources from which they can load<script> and <object> resources, and disallows potentially unsafe practices such as the use of eval(). See Default content security policy to learn more about the implications of this.

You can use the "content_security_policy" manifest key to loosen or tighten the default policy. This key is specified in just the same way as the Content-Security-Policy HTTP header. See Using Content Security Policy for a general description of CSP syntax.

For example, you can use this key to:

There are restrictions on the policy you can specify here:

  • The policy must include at least the script-src and the object-src directives, and the script-src directive must contain the keyword 'self'.
  • Remote sources must use https: schemes.
  • Remote sources must not use wildcards for any domains in the public suffix list (so "*" and "*" are not allowed, although "*" is allowed).
  • All sources must specify a host.
  • The only permitted schemes for sources are: blob:, filesystem:, moz-extension:, and https:.
  • The only permitted keywords are: 'none', 'self', and 'unsafe-eval'.


Valid examples

Allow remote scripts from "": (see note 1 )

"content_security_policy": "script-src 'self'; object-src 'self'"

Allow remote scripts from any subdomain of "":

"content_security_policy": "script-src 'self' https://*; object-src 'self'"

Allow eval() and friends:

"content_security_policy": "script-src 'self' 'unsafe-eval'; object-src 'self';"

Allow the inline script: "<script>alert('Hello, world.');</script>":

"content_security_policy": "script-src 'self' 'sha256-qznLcsROx4GACP2dm0UCKCzCG+HiZ1guq6ZZDob/Tng='; object-src 'self'"

Keep the rest of the policy, but also require that images should be packaged with the extension:

"content_security_policy": "script-src 'self'; object-src 'self'; img-src 'self'"

Require that all types of content should be packaged with the extension:

"content_security_policy": "default-src 'self'"

Invalid examples

Policy that omits the "object-src" directive:

"content_security_policy": "script-src 'self' https://*;"

Policy that omits the "self" keyword in the "script-src" directive:

"content_security_policy": "script-src https://*; object-src 'self'"

Scheme for a remote source is not https:

"content_security_policy": "script-src 'self'; object-src 'self'"

Wildcard is used with a generic domain:

"content_security_policy": "script-src 'self' https://*; object-src 'self'"

Source specifies a scheme but no host:

"content_security_policy": "script-src 'self' https:; object-src 'self'"

Directive includes the unsupported keyword 'unsafe-inline':

"content_security_policy": "script-src 'self' 'unsafe-inline'; object-src 'self'"

1. Note: Valid examples display the correct use of keys in CSP. However, extensions with 'unsafe-eval', 'unsafe-inline', remote script, or remote sources in their CSP are not allowed for extensions listed on due to major security issues.



Browser compatibility

ChromeEdgeFirefoxFirefox for AndroidOpera
Basic supportYesYes 148 248 2Yes
1. Only the default content security policy is supported: "script-src 'self'; object-src 'self';".
2. Firefox does not support '' or 'http://localhost' as script sources: they must be served over HTTPS.

Document Tags and Contributors

 Contributors to this page: andrewtruongmoz, erosman, wbamberg, fscholz, Makyen, kmaglione
 Last updated by: andrewtruongmoz,