CSP: connect-src

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

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.


One or more sources can be allowed for the connect-src policy:

Content-Security-Policy: connect-src <source>;
Content-Security-Policy: connect-src <source> <source>;


<source> can be any one of the values listed in CSP Source Values.

Note that this same set of values can be used in all fetch directives (and a number of other directives).


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

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

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

    navigator.sendBeacon("https://not-example.com/", {
      /* … */


Content Security Policy Level 3
# directive-connect-src

Browser compatibility

BCD tables only load in the browser

Compatibility notes

  • Prior to Firefox 23, xhr-src was used in place of the connect-src directive and only restricted the use of XMLHttpRequest.

See also