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Google's John Mueller calls changing parameters on sitemap URLs a bad idea
Asked on Bluesky about appending a changing timestamp parameter to sitemap URLs so search engines recrawl them every day, Google's John Mueller called the technique a bad idea and said it signals that a page's canonical URL keeps changing.
Image: Search Engine Journal
Why it mattersA trick that makes a page look new to a crawler also makes its address look unstable, which is the opposite of what a site needs to accumulate ranking and citations on one URL.
Search Engine Journal reported on 2 September that Google's John Mueller was asked about a sitemap technique on Bluesky and advised against it. The question came from the account @seoharbour.
The technique is sometimes called cache busting. Instead of relying on the <lastmod> element in an XML sitemap to tell a search engine when a page changed, the site appends a parameter that changes every day, such as a Unix timestamp, to each URL in the sitemap. Every URL then looks new on every fetch, which is intended to force a daily crawl.
What Mueller said
Mueller's answer, as quoted by Search Engine Journal, was direct. "I think that's a bad idea because you're signaling that the canonical URL for a piece of content should be constantly changing."
He added a second line: "Having clean, stable URLs is important."
Search Engine Journal attributes both quotes to Mueller's Bluesky reply. Google has not published anything else on the technique alongside this exchange, so his answer is the whole of the record here.
Why the reasoning matters more than the verdict
The problem Mueller names is a side effect rather than a penalty. A URL carrying a daily-changing parameter is a different address each day as far as canonicalisation is concerned. Everything a site is trying to build on one page, meaning the signals that accumulate against a single address, has to be reattributed rather than added to.
That reasoning is worth separating from the specific trick, because it applies to anything that varies a URL for a reason unrelated to the content at that URL. Session identifiers, tracking parameters and cache-busting timestamps all create the same problem, and only the last one is being presented as an optimisation.
Sitemap generation is usually part of the build pipeline, which means it is engineering's file rather than marketing's, and it rarely gets reviewed after the day it was written. This is a case where a plausible-sounding change to that script would work against the site.
The honest signal for freshness is the one already designed for it. <lastmod> should carry the real modification time of the page, and it is only useful to a crawler if it is accurate. A generator that stamps every entry with the build time tells a search engine nothing, because every page changed on every deploy. A generator that stamps each entry with the last time that page's content actually changed gives a crawler something to act on.
The other practical note is that forcing a crawl does not make a page more valuable to a search engine. Search engines decide how often to crawl by their own rules, and a page fetched daily but unchanged does not gain anything from the visit.
Source
Search Engine Journal, "Google Responds To Sitemap SEO Technique That Forces Daily Crawling"
This item was written by an AI system from the linked source. Reveneau is responsible for what it publishes.
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