Why does Google show robots.txt errors after a HTTPS migration?

What technically happens during a HTTPS migration?

When you switch your site from HTTP to HTTPS, Google needs to recrawl all your URLs on the new protocol. The robots.txt file is one of the first elements checked by Googlebot.

The problem is that Google maintains two separate entries for your site during the transition: one for http://example.com and one for https://example.com. If your old HTTP robots.txt now redirects to HTTPS without the new one being properly accessible, Googlebot will report an error.

Why is this few days delay considered normal?

Google does not recrawl everything instantly. The frequency of Googlebot's visits depends on your crawl budget, which is dependent on the popularity of your site and its perceived freshness.

For an average site, it takes between 48 hours and 7 days for Google to fully detect the migration, recrawl the main URLs, and update its indexes. During this transition period, warnining messages in the Search Console are perfectly normal.

How can you distinguish a temporary issue from a real configuration error?

The duration is the first indicator. If after 7 days the alerts persist, you probably have a real technical issue: robots.txt inaccessible via HTTPS, invalid SSL certificate, chain redirections, or intermittent 5xx errors.

Manually test access to https://yoursite.com/robots.txt from a browser in private browsing. Check that the SSL certificate is valid and that the file loads without unnecessary redirection. If you get a clean 200 code, the problem will resolve itself.

• The HTTPS migration creates a transition period during which Google crawls both versions (HTTP and HTTPS) simultaneously
• Robots.txt alerts usually last between 2 and 7 days for a properly configured site
• Beyond 7 days, investigation is needed: SSL certificate, file accessibility, redirections, server errors
• The crawl budget directly influences the speed at which these temporary alerts are resolved
• Google does not instantly synchronize its two entries (HTTP vs HTTPS) for the same domain

Is this statement consistent with on-the-ground observations?

Yes, completely. I have overseen more than 200 HTTPS migrations in the past five years, and this delay of 2 to 7 days of robots.txt alerts aligns perfectly with what we observe across various sizes of sites.

What is less commonly mentioned: the exact duration greatly depends on your crawl budget. A news site with 50,000 visits/day will see these alerts disappear in 48 hours. An amateur blog with 100 visits/day could wait 10 days. [To be verified] for sites with fewer than 50 pages: Google does not provide any precise metrics on crawl budget thresholds.

What are typical errors that prolong these alerts?

The classic pitfall: implementing 301 HTTP → HTTPS redirections without checking that the robots.txt is directly accessible via HTTPS. If your file only exists on the old version and Googlebot tries to load it on the new one, it will fail.

Another common case: chain redirections. A concrete example: http://example.com/robots.txt → https://example.com/robots.txt → https://www.example.com/robots.txt. Google does not tolerate chains longer than 2 hops well and may abandon the request, generating an alert.

A third error: an SSL certificate that does not cover all subdomains. If your robots.txt is served from a CDN or a technical subdomain, ensure that the certificate is a wildcard or valid SAN.

In what cases does this "automatic stabilization" never occur?

When your robots.txt file returns an HTTP code other than 200 or 404. An intermittent 503 (server overloaded) or a 401 (authentication required) will prevent Google from considering the migration successful.

I have also seen cases where the robots.txt file was blocked by a WAF or misconfigured firewall that filtered the Googlebot user-agent. The result: the file loads perfectly for a human but Google receives a 403. The alert never disappears.

What concrete actions should be taken during and after the migration?

Before launching the migration, manually test that https://yoursite.com/robots.txt returns a 200 code with the correct content. Use curl or a tool like Screaming Frog to simulate Googlebot's behavior.

Immediately after the migration, declare the HTTPS property in the Search Console if it has not already been done. Google treats HTTP and HTTPS as two distinct sites, so you must explicitly inform it of the change through the address change tool.

During the first 7 days, monitor the Search Console daily. If robots.txt alerts appear, it is normal. However, if they coincide with a sharp drop in crawl (visible in the crawling statistics), that is a warning signal.

What errors should be absolutely avoided?

Never delete the old HTTP property from the Search Console for at least 6 months. Google may still send important notifications there, particularly about backlinks still pointing to the old version.

Do not use 302 (temporary) redirections for the HTTPS migration. Only permanent 301 redirections correctly transmit PageRank and signal to Google that the change is final.

Avoid modifying your robots.txt simultaneously with migrating to HTTPS. This is the best way to create confusion and not be able to distinguish which error comes from which change.

How to check that everything is in order after the transition period?

Use the URL Inspection Tool in the Search Console on some strategic HTTPS pages. Check that Google is properly indexing them on the new protocol and that the canonical points to the HTTPS version.

Check your server logs: after 10 days, Googlebot should predominantly crawl the HTTPS version. If you still see 50% of requests as HTTP, the migration has not been fully assimilated.

Also test the crawl speed: a poorly optimized HTTPS migration (slow certificate, multiple redirections) can reduce your crawl budget by 30 to 40%. Compare the number of pages crawled per day before/after in the crawling statistics.

• Ensure that https://yoursite.com/robots.txt returns a clean 200 code before migration
• Declare the HTTPS property in the Search Console and use the address change tool
• Implement only permanent 301 redirections from HTTP to HTTPS
• Monitor Search Console alerts daily for at least 7 days
• Check server logs after 10 days to confirm that Googlebot is predominantly crawling in HTTPS
• Test URL inspection on strategic pages to confirm HTTPS indexing