A Reddit thread about a sharp crawl drop drew a response from Google’s John Mueller. He suggests sudden declines usually indicate 429/500/503 or timeouts, not 404s.
What Happened
In the thread, the poster said crawl requests fell by about 90% within 24 hours of deploying broken hreflang URLs in HTTP headers.
The hreflang URLs reportedly returned 404s when Googlebot tried to fetch them.
They wrote:
“Last week, a deployment accidentally added broken hreflang URLs in the Link: HTTP headers across the site:
- Googlebot crawled them immediately → all returned hard 404s.
- Within 24h, crawl requests dropped ~90%.
- Indexed pages are stable, but crawl volume hasn’t recovered yet”
What Mueller said
Mueller questioned whether 404s alone would cause such a rapid drop and pointed to server-side issues as a likelier explanation.
Mueller wrote:
“I’d only expect the crawl rate to react that quickly if they were returning 429 / 500 / 503 / timeouts, so I’d double-check what actually happened (404s are generally fine & once discovered, Googlebot will retry them anyway). For example, if it was a CDN that actually blocked Googlebot, then you need to make sure that’s resolved too. Once things settle down on the server, the crawl rate will return to normal automatically. (There’s no defined time, and intuitively – I don’t know if this is the case here – reducing crawl rate makes sense to do quickly to resolve an immediate issue, and increasing crawl rate makes sense to do cautiously).”
This aligns with Google’s documented crawl management guidance.
If you need to throttle crawling for a short period, Google recommends returning 500, 503, or 429 responses. 403/404 aren’t listed for that purpose. For more, see Google’s guidance on reducing crawl rate.
Related: Google On The SEO Impact Of 503 Status Codes
Next Steps
When crawl requests dive suddenly, verify what your servers and CDN returned to Googlebot during the window:
- Check logs and Search Console’s Crawl Stats for spikes in 429/500/503 or timeouts.
- Confirm that a CDN, WAF, or rate limiter didn’t gate Googlebot.
- Validate that the reported 404s are the dominant signal and not coincidental.
Remember that recovery isn’t immediate. Mueller indicated crawl rates return to normal automatically after server-side problems are resolved, with no fixed timeline.
See also: Google explains why graphs in Search Console fluctuate
Featured Image: Roman Samborskyi/Shutterstock
