Understanding False Positives in HTTP 405 Error Reporting: A Case Study
Introduction
Managing a large website with thousands of URLs can be a complex and challenging task, especially when it comes to accurately diagnosing server response issues. One common pitfall is the misinterpretation of HTTP status codes, which can lead to unnecessary concern or misguided troubleshooting efforts. In this article, we explore a real-world scenario involving a retail client with extensive URL coverage, where diagnostic tools report a high incidence of 405 errors, despite the pages loading correctly for users. We will discuss potential causes, including server configurations and bot blocking, and clarify how to interpret such discrepancies.
The Scenario
The client operates a retail website comprising approximately 160,000 URLs. A site audit utilizing Screaming Frog SEO Spider indicates that around 48% of these URLs return a 405 status code. However, user experience evidence and actual page loads suggest otherwise; the pages load successfully with a 200 OK status. This discrepancy raises questions about the accuracy of the crawl data and whether the reported errors reflect reality or are false positives.
Potential Causes of Misreported 405 Errors
- Bot Blocking and Server Configuration
One plausible explanation is that the server is actively blocking certain automated requests, such as those from crawlers or bots, based on IP addresses or user-agent strings. Servers often implement security measures that restrict or alter responses to non-human traffic. For instance, some servers may generate 405 Method Not Allowed responses when they detect suspicious or automated activity. Importantly, these restrictions might only affect non-browser requests, while legitimate users and search engine bots with proper credentials or configurations can access the pages without issue.
- Request Method Issues
The HTTP method used during crawling could differ from standard GET requests. Some crawlers might send requests with uncommon HTTP methods, prompting the server to respond with a 405 error. Alternatively, servers configured to accept only certain methods may respond with 405 for unsupported request types. If the crawler’s headers or request setup don’t align with those of real browsers, this can lead to mismatched status codes.
- Javascript-Heavy Pages and Bot Behavior
On the frontend, tools like Google PageSpeed Insights sometimes report “NO_FCP” (No First Contentful Paint) errors on desktop. This issue can stem from heavy client-side Javascript or server-side rendering issues, which may delay or prevent the loading of initial content during automated scans. Interestingly, mobile versions of the site tend to render correctly, potentially