A browser will enter into a secure context when it has met its minimum requirements of being secure. Secure contexts allow the browser to expose APIs that should only be permitted when transferred securely to the user.

Why should some features be restricted? 

Some APIs on the web are very powerful giving an attacker the ability to do the following and more:

  • Invade a user's privacy.
  • Get low level access to a user's computer.
  • Get access to data like user credentials.

When is a context considered secure?

A context will be considered secure when it's delivered securely or locally. A context that isn't top-level browser context (a page that isn't framed in any way) must have only secure context parents.

Locally delivered files such as http://localhost and file:// paths are considered secure.

Contexts that are not local must be served over https:// or wss:// and where the protocols used should not be considered deprecated. 

Feature detection

Pages can use feature detection to check whether they are in a secure context or not by using the isSecureContext boolean which is exposed on the global scope.

if (window.isSecureContext) {
  // Page is a secure context so service workers are now available
  navigator.serviceWorker.register("/offline-worker.js").then(function () {

What APIs require secure contexts?

Draft proposals


Some browsers may decide to opt for certain APIs into being secure context only such as Chrome issues deprecation warnings when not in a secure context for the following:


Specification Status Comment
Secure Contexts Working Draft Editor’s Draft

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support (Yes) 49 (49) ? ? ?
Feature Android Android Webview Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support No support (Yes) 49.0 (49) ? ? ? (Yes)

See also

Document Tags and Contributors

 Contributors to this page: fscholz, cpeterson, rolfedh, PushpitaPikuDey, jonathanKingston
 Last updated by: fscholz,