Connection allowlistsLimited availability

The Connection-Allowlist HTTP response header limits which requests a page may initiate using fetch and other APIs.

Not yet supported in all major browsers — check the table and provide a fallback.

How to use ↓Compare browsers

Browser support

DesktopChrome

1–151Not supported

152+Supportedsince Aug 25, 2026

Current: 155

Edge

12–151Not supported

152+Supportedsince Aug 28, 2026

Current: 154

Firefox

✕Not supportedup to 157

Current: 157

Safari

✕Not supportedup to 27

Current: 27

MobileChrome Android

18–151Not supported

152+Supportedsince Aug 25, 2026

Current: 155

Firefox Android

✕Not supportedup to 157

Current: 157

Safari iOS

✕Not supportedup to 27

Current: 27

How to use

Not supported in Firefox, Safari, Firefox Android, Safari iOS. Use feature detection below and provide a fallback (or a polyfill) for those browsers.

Example

Full syntax and examples are on MDN — see the links below.

Feature detection

JS · check before using

if ("ReportingObserver" in globalThis && "ReportingObserver" in ReportingObserver.prototype) {
  // ReportingObserver.ReportingObserver is available
}

Specification

wicg.github.io/connection-allowlists ↗

Sub-features

Support for each part of the feature (3). The overall table above shows when the whole feature works.

Sub-feature	Chrome	Edge	Firefox	Safari	Chrome Android	Firefox Android	Safari iOS
ReportingObserver.ReportingObserver.options_parameter.types_property.connection-allowlist	152	152	✕	✕	152	✕	✕
http.headers.Connection-Allowlist	152	152	✕	✕	152	✕	✕
http.headers.Connection-Allowlist-Report-Only	152	152	✕	✕	152	✕	✕