Google Search Central is reminding anyone who takes servers offline for PHP patches to return a 503 status code, which tells Google the outage is temporary.<\/p>\n
The LinkedIn post<\/a> went up Wednesday, the day PHP released emergency fixes for two critical\u00a0<\/a>flaws\u00a0<\/a>that\u00a0can let attackers run code without logging in.<\/p>\n The post doesn\u2019t say how long a 503 can stay up. Google\u2019s crawl rate documentation<\/a> recommends against serving one for more than one to two days, because URLs that return it for multiple days may be dropped from the index.<\/p>\n What Google And Mueller Said<\/p>\n Google Search Central wrote:<\/p>\n \u201cServing a 503 (Service Unavailable) HTTP status code ensures already indexed URLs are preserved in Search while you work. Once you start serving 200 responses again, things naturally return to normal.\u201d<\/p>\n The post also warned against generic 404s or 200 error pages during the downtime. It linked to Google\u2019s page on how HTTP status codes affect its crawlers<\/a>.<\/p>\n In a 2013 post<\/a>, Google\u2019s John Mueller wrote that returning an error page with a 200 OK status code causes Google to index that error content.<\/p>\n Mueller posted his own reminder on Bluesky<\/a> earlier Wednesday and said where the 503 can come from:<\/p>\n \u201cIf you\u2019re taking PHP sites down to schedule time to deal with \u201cunplanned updates\u201d, use HTTP 503 instead of letting responses time out \/ 404 \/ 500. You can do this outside of PHP \/ point DNS elsewhere \/ CDN.\u201d<\/p>\n The 2011 Google post<\/a> he linked shows how to send a 503 with PHP code, which won\u2019t help when PHP is what\u2019s coming down.<\/p>\n In a reply, a Bluesky user ranked the responses roughly, from best to worst, as 503, 500, 403, 404 and 200. Mueller called it \u201ca good model.\u201d<\/p>\n How 503s Affect Crawling<\/p>\n Google\u2019s crawl rate documentation lists 500, 503, and 429 responses as the way to urgently reduce crawler traffic for a short period. When Google\u2019s crawlers hit a large number of URLs returning those status codes, they reduce the crawl rate across the entire hostname, including URLs that still return content. Once the number of errors drops, Google automatically increases the crawl rate again.<\/p>\n When returning a 503 or 429, you can add a Retry-After HTTP header that tells Google\u2019s crawlers when to try again, either as a number of seconds or as a date and time in UTC.<\/p>\n Google\u2019s crawl rate page also warns that slower crawling means Googlebot discovers fewer new pages and refreshes existing ones less often. Google Ads campaigns may be canceled or paused.<\/p>\n