Why do so many sites lose traffic after transitioning to HTTPS, even with redirects in place?

Why does Google keep emphasizing HTTPS migrations when it's supposed to be a done deal?

Because on the ground, one in three HTTPS migrations goes wrong. Technical teams often think that simply installing an SSL certificate is enough. As a result, HTTP and HTTPS versions coexist, the crawl budget is inflated, and signals are diluted between the two versions of the site.

Google continues to see sites that leave both versions running without systematic 301 redirects. Or worse, sites that configure temporary 302 redirects which don't pass any ranking signals. The search engine is left with two URLs for each page and must choose which version to index. Spoiler: it's not always the one you want.

What really causes an HTTPS migration to fail from an SEO perspective?

The first pitfall is the redirect chain. You switch from HTTP to HTTPS, but if your old site already had internal redirects, you end up with chains that are three or four links deep. Googlebot will follow them, but reluctantly. And each link consumes crawl budget.

The second issue arises from mixed content. Your HTML is in HTTPS, but your images, CSS, or scripts are still being called in HTTP. Browsers block these, Google sees broken pages, and user experience diminishes. And if your certificate is not installed correctly or expires, you enter immediate red alert in Chrome.

What specific role does Search Console play in this monitoring?

Search Console allows you to detect coverage errors specific to the HTTPS version. You need to add the new HTTPS property as a distinct entity and ensure that Google is properly crawling this version, not the old one.

This is where you can identify orphan pages that don’t redirect, SSL certificate errors seen by Googlebot, and especially indexing evolution between the two versions. If after two weeks you're still seeing 80% of your URLs indexed in HTTP, it means your migration hasn’t taken.

• Permanently required 301 redirect for the entire site, not just the homepage
• Valid SSL certificate that is up-to-date with a complete certification chain
• Distinct HTTPS property in Search Console to monitor the indexing switch
• Mixed content verification: no HTTP resources should remain on HTTPS pages
• Redirect chain audit to avoid multiple jumps that consume crawl budget

Does this recommendation from Google truly reflect what happens on the indexing side?

Absolutely. In migrations I have audited post-mortem, 90% of traffic drops stemmed from a shaky redirect configuration. Google isn’t making this up: this is basic knowledge, but it’s precisely this basic knowledge that is frequently overlooked by DevOps who are unaware of SEO stakes.

One point that Google doesn't emphasize enough: the HTTPS migration is not limited to server redirects. Internal links often remain in HTTP after the switch. Googlebot follows the redirects, but you're wasting crawl budget unnecessarily. And if you have millions of pages, this waste becomes critical.

What are the gray areas that Google doesn't mention here?

Google remains vague on the speed of re-crawl and re-indexation. In theory, 301 redirects pass along PageRank. In practice, I've seen sites take four to six weeks before the HTTPS version becomes predominant in the index. [To be verified]: Google provides no SLA on this transition.

Another silence: the issue of external backlinks. Your partners, directories, and press mentions link to your URLs in HTTP. Google follows the redirects, but those links lose some value with each jump. Ideally, you would contact the sources to update the links. But in reality, no one does it 100%. Google's statement says nothing about this diffuse signal loss.

In what cases could this HTTPS migration turn disastrous?

On large sites with custom CDNs, configuration errors proliferate. You may have subdomains that don't switch to HTTPS, and sections of the site served by different servers that don't all have the same certificate. As a result, Google ends up indexing a heterogeneous mix of HTTP and HTTPS versions.

E-commerce sites are particularly vulnerable. If you have facets and filters that generate thousands of URLs, and your redirects do not cover these combinations, Google will crawl duplicate pages. The dilution of ranking is immediate. I've seen a site lose 40% of its organic traffic over three months because the redirects only covered canonical URLs, not the parameterized variants.

What should you check before launching the HTTPS switch?

Start with a complete audit of your current redirects. If you already have 301s in place (for previous redesigns, changed URLs), map them all out. The goal is to avoid redirect chains that are three levels deep or more. Googlebot will follow, but you'll waste crawl budget unnecessarily.

Next, test your SSL certificate locally or in a pre-production environment. Check that the certification chain is complete, and that the certificate covers all your subdomains if you're using a wildcard. Use tools like SSL Labs to validate the configuration before going live.

How can you ensure that the migration doesn't break indexing?

Deploy your 301 redirects in one wave, not progressively. Google hates hybrid situations where part of the site is in HTTPS and the other is still in HTTP. If you must do a phased rollout for technical reasons, start with low-traffic sections to test.

Immediately add the HTTPS property in Search Console and submit a new XML sitemap pointing to the HTTPS URLs. Keep the old HTTP property active for at least three months to compare indexing trends. If HTTPS indexing doesn't take off after two weeks, it's a red flag.

What post-migration errors should you prioritize checking?

The first error is mixed content. Crawl your site with Screaming Frog or an equivalent tool to detect all resources (images, JS, CSS, iframes) still called in HTTP. Chrome and Firefox block these contents; Google sees them as negative UX signals.

Next, monitor SSL certificate errors in Search Console. Google will highlight pages where it detects issues with the certificate. If your certificate expires or the certification chain is incomplete, Googlebot may refuse to crawl some sections of your site. Lastly, check that your internal links point directly to HTTPS, not to HTTP with redirect.

• Audit all existing redirects to avoid chains three levels deep or longer
• Test the SSL certificate in pre-production with SSL Labs before going live
• Deploy 301 redirects in one wave across the entire site
• Add the HTTPS property in Search Console and submit an HTTPS sitemap
• Crawl the site post-migration to detect any mixed content (HTTP resources on HTTPS pages)
• Update all internal links to point directly to HTTPS without redirection