Google advised webmasters globally to use the 503 (Service Unavailable) HTTP status code during temporary server downtime to maintain search engine indexing of their websites.
The recommendation followed recent emergency security patches for critical vulnerabilities in PHP, a widely used scripting language, which allowed attackers to execute code without authentication.
John Mueller, a Search Advocate at Google, emphasized the importance of correctly signaling server status to search engine crawlers, noting that a 503 status code informs Google that the downtime is temporary, preventing URLs from being removed from the index.
Google cautioned against employing generic 404 (Not Found) or 200 (OK) status codes during maintenance, stating that a 200 status code, even when displaying an error page, can lead to Google indexing the error content itself, according to Google Search Central guidelines.
The 503 status code should not be deployed for extended periods, Google indicated, as URLs returning a 503 for more than one to two days might eventually be dropped from its search index.
For the 503 response to be effective, it must originate from a system that remains operational while the primary server, such as one running PHP, is offline, Google suggested, citing a content delivery network (CDN) or a temporary server as examples.
Additionally, the robots.txt file, which directs search engine bots, should continue to respond normally during the downtime, Google said.
Vahan Petrosyan, a technical SEO consultant, highlighted the practical implications of Google’s advice, noting that proper status code implementation is important for SEO during maintenance windows.
Webmasters can also include a ‘Retry-After’ HTTP header with a 503 or 429 (Too Many Requests) response, which can instruct Google’s crawlers on when to attempt re-crawling the site, potentially optimizing the re-indexing process.
Gary Illyes, a Google Search Relations analyst, previously underscored the significance of clear communication with crawlers regarding server availability and temporary issues.
Source: Search Engine Journal
