Mixed Content Warnings: What They Are and How to Fix Them
Understand mixed content on HTTPS pages, why browsers block it, and the practical fixes that stop insecure HTTP assets from undermining your secure site.
What mixed content means
A mixed content warning appears when an HTTPS page loads one or more resources over plain HTTP. The page itself may have a valid certificate, but the browser still sees an insecure request for something inside that page, such as an image, script, stylesheet, font, iframe, or API call. That weakens the promise that the page is fully protected in transit.
In practice, mixed content HTTPS issues often show up after a migration from HTTP to HTTPS, a theme update, or a plugin that still outputs old asset URLs. A page can look mostly fine while quietly requesting insecure content in the background. That is why users can see warnings even when the main URL begins with `https://` and the certificate is valid.
Why browsers block it
Modern browsers treat active mixed content, especially scripts, styles, and iframes, as a serious risk because those resources can change how the page behaves. If they travel over HTTP, an attacker on the network could tamper with them before they reach the browser. To reduce that risk, browsers now block many of these requests by default instead of merely showing a soft warning.
Passive mixed content, such as images, may be upgraded or handled less aggressively depending on the browser, but it still creates avoidable trust and consistency problems. The important point is that a secure page is only as strong as the resources it loads. One insecure dependency can turn a clean HTTPS setup into a confusing experience for visitors and support teams.
Common causes of HTTP content on an HTTPS page
The most common cause is hard-coded `http://` URLs in templates, CMS fields, or old content. You also see mixed content after CDN changes, third-party embeds, analytics snippets, or image libraries that were never updated to protocol-relative or HTTPS URLs. Legacy asset hosts are another frequent culprit, especially on sites that have been through several redesigns.
Backend code can create the same issue. A reverse proxy might terminate TLS correctly for the main request, but application code can still generate insecure asset links if it believes the original request was HTTP. When you are trying to fix a mixed content warning, you need to check both the page source and the systems that generate asset URLs, not just the certificate itself.
How to fix mixed content warnings for good
Start by identifying every insecure request the page makes. Browser developer tools will usually list blocked or downgraded resources. Replace those `http://` links with `https://` versions wherever the resource is available securely. If a third-party asset host does not support HTTPS, the long-term fix is to remove, proxy, or replace that dependency instead of trying to work around the browser.
After the update, rerun an external security check to confirm the page loads cleanly over HTTPS and that redirects and headers still look healthy. Https Co is a simple way to review the broader setup once you think you have fixed the issue. That matters because mixed content often travels with other HTTPS gaps, and it is better to catch them in the same pass.
Check your page for broader HTTPS issues
Use the Https Co security checker after fixing mixed content to confirm the certificate, redirects, and browser-facing protections still look healthy.