Content-Security-Policy: worker-src directive

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨May 2022⁩.

The HTTP Content-Security-Policy (CSP) worker-src directive specifies valid sources for Worker, SharedWorker, or ServiceWorker scripts.

CSP version	3
Directive type	Fetch directive
Fallback	If this directive is absent, the user agent will first look for the `child-src` directive, then the `script-src` directive, then finally for the `default-src` directive, when governing worker execution.

Syntax

http

Content-Security-Policy: worker-src 'none';
Content-Security-Policy: worker-src <source-expression-list>;

This directive may have one of the following values:

'none'

No resources of this type may be loaded. The single quotes are mandatory.

<source-expression-list>

A space-separated list of source expression values. Resources of this type may be loaded if they match any of the given source expressions. For this directive, the following source expression values are applicable:

Examples

Violation cases

Given this CSP header:

http

Content-Security-Policy: worker-src https://example.com/

Worker, SharedWorker, ServiceWorker are blocked and won't load:

html

<script>
  let blockedWorker = new Worker("data:text/javascript,…");
  blockedWorker = new SharedWorker("https://not-example.com/");
  navigator.serviceWorker.register("https://not-example.com/sw.js");
</script>