Support in current browsers

Checked against the current browser versions recorded in MDN browser data 8.0.7.

BrowserMinimumOutcomeReason
Chrome150WorksEvery required mapped BCD feature is available without a recorded qualification.
Edge150WorksEvery required mapped BCD feature is available without a recorded qualification.
Firefox152WorksEvery required mapped BCD feature is available without a recorded qualification.
Safari26.5WorksEvery required mapped BCD feature is available without a recorded qualification.
Chrome for Android150WorksEvery required mapped BCD feature is available without a recorded qualification.
Firefox for Android152WorksEvery required mapped BCD feature is available without a recorded qualification.
Safari on iOS26.5WorksEvery required mapped BCD feature is available without a recorded qualification.
Android WebView150WorksEvery required mapped BCD feature is available without a recorded qualification.
Samsung Internet29.0WorksEvery required mapped BCD feature is available without a recorded qualification.

What this feature can and cannot do

Helps protect against

  • Mixed-content downgrade
  • Accidental insecure subresource requests

Does not guarantee

  • Unavailable HTTPS resources
  • Insecure external redirects
  • Transport setup

What you need before using it

  • HTTPS availability for every upgraded resource

Fallback to keep in place

Migrate every resource URL to HTTPS and block mixed content explicitly.