Is it really necessary to fill in the priority and changefreq fields in your XML sitemaps?

Why were these two fields invented if Google ignores them?

The XML sitemap protocol dates back to 2005, the result of collaboration between Google, Yahoo, and Microsoft. At that time, search engines were looking for signals to prioritize crawling. The priority (0.0 to 1.0) and changefreq (daily, weekly, monthly…) fields were designed to guide bots to important and frequently updated pages.

However, webmasters massively cheated. Predictable result: 90% of sites were setting priority="1.0" everywhere and changefreq="daily" even on pages that had been dead for three years. Google eventually completely ignored these signals, which became noise.

What does "lastmod is the only important field" actually mean?

The lastmod attribute indicates the last modification date of a URL. When correctly populated, it allows Googlebot to detect changes without having to fully re-crawl each page. This is a gain in efficiency for your crawl budget, especially on large sites.

Be careful: lastmod should only reflect substantial content changes. Automatically modifying the date with each bot visit or each CSS refresh breaks Google's trust. If you lie about lastmod, Google will eventually ignore it too — and you'll lose the only reliable signal you had left.

Does this statement apply to all search engines?

No, and this is a trap. Bing and other search engines still sometimes read priority and changefreq, even if their impact remains marginal. Some SEO monitoring tools also use these fields for their own dashboards.

But let's be honest: if you're optimizing for Google (95%+ of organic traffic in France), these fields are a waste of time. Keep them empty or set by default, no one will hold it against you.

• Priority and changefreq have been ignored by Google for years
• Lastmod remains the only useful signal for optimizing crawl budget
• Only fill lastmod in case of real and substantial content changes
• Bing and a few secondary engines still read priority/changefreq, but the impact is negligible
• A minimalist sitemap (URL + reliable lastmod) is better than a sitemap overloaded with false data

Is this statement consistent with observed practices in the field?

Absolutely. Laboratory tests and crawl observations have shown since 2019-2020 that no variation in priority or changefreq affects the crawling frequency of Googlebot. Even on sites with a tight crawl budget, modifying these values doesn’t change the crawl curves in Search Console.

On the other hand, a consistent lastmod does indeed accelerate update detection. On a news site with 50,000 articles, moving from a generic lastmod to a precise lastmod (based on the actual modification date) reduced the average indexing delay of updates by 40%. But this observation remains [To be verified] on a large scale — Google does not publish official benchmarks.

What nuances should be added to this statement?

First point: lastmod is only useful if your CMS generates reliable dates. WordPress, for example, updates lastmod as soon as a comment is posted or a plugin modifies a meta tag. Result: Google receives erratic signals and ends up ignoring them. A system that tracks true editorial modifications is necessary.

Second nuance: on very small sites (under 500 pages), lastmod has nearly zero impact. Google crawls everything regularly anyway. Sitemap optimization becomes relevant starting from a few thousand URLs, when the crawl budget really becomes a constraint.

In what cases does this rule not apply?

If you manage a multilingual international site with versions for Yandex, Baidu, or Naver, those engines have their own rules. Yandex, in particular, still seems to take changefreq into account in some sectors. But we lack solid data — [To be verified] through dedicated tests.

Another edge case: video or image sitemaps. Here, other specific attributes (video:publication_date, image:caption…) come into play. Lastmod remains relevant, but priority/changefreq remain useless even in these extended formats.

What should you actually do with your XML sitemaps?

First action: audit the reliability of your lastmod attribute. Take 20 random URLs, manually check the actual last modification date of the content, and compare it with the value in the sitemap. If you notice systematic discrepancies (lastmod changing without reason, or never changing even after a real update), correct the generation logic.

Next, simplify. Remove scripts that calculate priority values based on page depth, traffic, or whatever metric. Keep a minimalist structure: URL + lastmod + optionally image/video if relevant. Fewer data = less risk of error = more trust from Google.

What errors should be avoided in managing lastmod?

Classic mistake: updating lastmod during cosmetic changes (typo fix, adding an internal link without editorial value). Google detects these micro-variations and ends up ignoring your signals. Reserve the change of lastmod for substantial updates — redesigning a section, adding significant content, major factual corrections.

Another trap: CMS that generate a new lastmod with every rebuild of the site, even if the content hasn’t changed. Some static site generators (Gatsby, Hugo…) fall into this trap. Configure your build to only touch lastmod if the source file has actually changed.

How to check if your sitemap is being correctly utilized by Google?

Use the Sitemaps report in Search Console. Google indicates how many URLs it has discovered, how many are indexed, and if it detects errors there. If you see a large gap between submitted URLs and discovered URLs, dig deeper — often it’s a problem with XML format or a malformed lastmod tag.

Also test the speed of change detection. Modify a page, update its lastmod, submit the sitemap via Search Console, and observe the time before Googlebot passes. On a healthy site with a good crawl budget, this takes a few hours to 2-3 days. If it lingers for a week, your lastmod is probably being ignored.

• Remove or leave the priority and changefreq fields empty in all your sitemaps
• Ensure lastmod reflects only substantial editorial changes
• Audit 20-30 URLs to validate coherence between lastmod and true modification date
• Configure the CMS/build to prevent parasitic automatic updates to lastmod
• Monitor the Sitemaps report in Search Console to detect formatting errors
• Test Googlebot's responsiveness after a modification + sitemap submission