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Mixed Content Blocked — HTTP Resources on HTTPS Page Blocked by Browser

Warningsecurity

Overview

Fix mixed content warnings and blocked resources when an HTTPS page loads images, scripts, or other resources over insecure HTTP connections.

Key Details

  • Mixed content occurs when an HTTPS page loads sub-resources (scripts, images, CSS) over HTTP
  • Active mixed content (scripts, iframes) is blocked by default in all modern browsers
  • Passive mixed content (images, audio, video) shows a warning but may still load
  • Mixed content breaks the security guarantee of HTTPS — attackers could modify HTTP resources
  • Content-Security-Policy: upgrade-insecure-requests header automatically upgrades HTTP to HTTPS

Common Causes

  • Website HTML contains hardcoded http:// URLs for images, scripts, or stylesheets
  • Third-party embed or widget loaded over HTTP on an HTTPS page
  • CMS (WordPress) database contains old http:// URLs from before HTTPS migration
  • CDN or external resource does not support HTTPS

Steps

  1. 1Open browser DevTools (F12) > Console to see which resources are blocked as mixed content
  2. 2Update resource URLs from http:// to https:// or use protocol-relative //example.com/resource
  3. 3For WordPress: use a search-replace plugin to update all http:// URLs in the database to https://
  4. 4Add Content-Security-Policy: upgrade-insecure-requests header to automatically upgrade HTTP to HTTPS
  5. 5If the third-party resource does not support HTTPS, proxy it through your own HTTPS server

Tags

mixed-contenthttpssecurityblockedupgrade

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Frequently Asked Questions

Active mixed content (scripts, stylesheets, iframes) can modify the page and is always blocked. Passive mixed content (images, audio, video) cannot execute code and is usually displayed with a warning but not blocked.