Really Simple SSL

How to use the Feature Policy header

The Permissions-Policy HTTP header replaces the existing Feature-Policy header for controlling delegation of permissions and powerful features. The header uses a structured syntax, and allows sites to more tightly restrict which origins can be granted access to features. This will be released in Really Simple SSL 4.1 before deprecation.

What is the Feature Policy header?

The Feature Policy header is a security header that controls which browser features can be used. Besides implementing these rules for your own content it can also prevent external iFrames from using these browser features, making it a powerful header to secure your site.

This allows you to have fine-grained control over which browser functions your site can use. There are a lot of directives that can be controlled with the Feature Policy header. For an extensive overview of all directives, refer to this list by Mozilla.

Each directive can have one of these three values:

  • * (this feature is allowed for your entire site, including external iFrames)
  • self (this feature is allowed for content coming from your own domain, blocking this feature for external iframes)
  • none (this feature is not allowed on your site at all)

How to use the Feature Policy header generator

You can find the Feature Header policy settings in the Premium tab from your Really Simple SSL Dashboard (Settings->SSL->Premium). To enable the Feature Policy header, enable the ‘Feature Policy‘ option. Once enabled, a new block containing a list of directives and their values will appear. By default, all directives will have the * value. You can change the value for each directive:

After pressing the ‘Save’ button near the bottom of the page, the Feature Policy will be automatically updated in your .htaccess file.

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