---
title: 'CSP: worker-src'
slug: Web/HTTP/Headers/Content-Security-Policy/worker-src
translation_of: Web/HTTP/Headers/Content-Security-Policy/worker-src
---
<div>{{HTTPSidebar}}</div>

<p>The HTTP {{HTTPHeader("Content-Security-Policy")}} (CSP) <code><strong>worker-src</strong></code> directive specifies valid sources for {{domxref("Worker")}}, {{domxref("SharedWorker")}}, or {{domxref("ServiceWorker")}} scripts.</p>

<table class="properties">
 <tbody>
  <tr>
   <th scope="row">CSP version</th>
   <td>3</td>
  </tr>
  <tr>
   <th scope="row">Directive type</th>
   <td>{{Glossary("Fetch directive")}}</td>
  </tr>
  <tr>
   <th scope="row">Fallback</th>
   <td>
    <p>If this directive is absent, the user agent will first look for the {{CSP("child-src")}} directive, then the {{CSP("script-src")}} directive, then finally for the {{CSP("default-src")}} directive, when governing worker execution.</p>

    <p>Chrome 59 and higher skips the {{CSP("child-src")}} directive.</p>

    <p>Edge 17 skips the {{CSP("script-src")}} directive (<a href="https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/17415478/">bug</a>).</p>
   </td>
  </tr>
 </tbody>
</table>

<h2 id="Syntax">Syntax</h2>

<p>One or more sources can be allowed for the <code>worker-src</code> policy:</p>

<pre class="syntaxbox notranslate">Content-Security-Policy: worker-src &lt;source&gt;;
Content-Security-Policy: worker-src &lt;source&gt; &lt;source&gt;;
</pre>

<h3 id="Sources">Sources</h3>

<p>{{page("Web/HTTP/Headers/Content-Security-Policy/connect-src", "Sources")}}</p>

<h2 id="Examples">Examples</h2>

<h3 id="Violation_cases">Violation cases</h3>

<p>Given this CSP header:</p>

<pre class="brush: bash notranslate">Content-Security-Policy: worker-src https://example.com/</pre>

<p>{{domxref("Worker")}}, {{domxref("SharedWorker")}}, {{domxref("ServiceWorker")}} are blocked and won't load:</p>

<pre class="brush: html notranslate">&lt;script&gt;
  var blockedWorker = new Worker("data:application/javascript,...");
  blockedWorker = new SharedWorker("https://not-example.com/");
  navigator.serviceWorker.register('https://not-example.com/sw.js');
&lt;/script&gt;</pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>{{specName("CSP 3.0", "#directive-worker-src", "worker-src")}}</td>
   <td>{{Spec2('CSP 3.0')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<p>{{Compat("http.headers.csp.Content-Security-Policy.worker-src")}}</p>

<h2 id="See_also">See also</h2>

<ul>
 <li>{{HTTPHeader("Content-Security-Policy")}}</li>
 <li><a href="/docs/Web/API/Web_Workers_API/Using_web_workers#Content_security_policy">CSP for Web Workers</a></li>
 <li>{{domxref("Worker")}}, {{domxref("SharedWorker")}}, {{domxref("ServiceWorker")}}</li>
</ul>