CSP: connect-src

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since August 2016.

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

http
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:

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

The following connections are blocked and won't load:

html
<a ping="https://not-example.com">
  <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></a
>

Specifications

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

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
connect-src

Legend

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Full support
Full support
Partial support
Partial support
Has more compatibility info.

See also