Headers: CSP.connect-src

Content-Security-Policy: connect-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 November 2016.

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See full compatibility

The HTTP Content-Security-Policy (CSP) connect-src directive restricts the URLs which can be loaded using script interfaces. The following APIs are controlled by this directive:

Note: connect-src 'self' does not resolve to websocket schemes in all browsers, more info in this issue.

CSP version	1
Directive type	Fetch directive
`default-src` fallback	Yes. If this directive is absent, the user agent will look for the `default-src` directive.

Syntax

Content-Security-Policy: connect-src 'none';
Content-Security-Policy: connect-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:

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

The following connections are blocked and won't load:

<a ping="https://not-example.com" href="/">Link</a>
<script>
  const response = fetch("https://not-example.com/");

  const xhr = new XMLHttpRequest();
  xhr.open("GET", "https://not-example.com/");
  xhr.send();

  const ws = new WebSocket("wss://not-example.com/");

  const es = new EventSource("https://not-example.com/");

  navigator.sendBeacon("https://not-example.com/", {
    /* … */
  });
</script>

Specifications

Specification
Content Security Policy Level 3> # directive-connect-src>

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	WebView on iOS
`connect-src`	25	14	50 23–50 Before Firefox 50, ping attributes of <a> elements weren't covered by connect-src.	15	7	25	23	14	7	1.5	4.4	7