Sitemap tooling has quietly shed several features that used to be standard. If your generator still emits them, it is doing work that nothing reads.
The old habit of firing a GET at a search engine's /ping?sitemap= URL after every deploy no longer does anything — Google retired that endpoint, and the recommended discovery path is now the Sitemap: directive in robots.txt plus a one-time submission in Search Console. If your deploy pipeline still pings, delete the step. Engines recrawl sitemaps on their own schedule, and for a site publishing a few times a week that is entirely sufficient.
Both fields are ignored by the major engines. They remain valid in the schema, so emitting them breaks nothing, but a generator that carefully computes a priority score is computing a number nobody reads. Modern generators drop them by default and put the effort into lastmod instead, which is the one hint that still influences recrawl behaviour — provided it is truthful.
Engines have become explicit that they use lastmod only when a site's values look consistent and honest. The failure mode is a build-time timestamp applied to every URL, which makes the whole file's dates change on every deploy and gets the field discounted site-wide. A good generator derives the value from content — the file's last content commit, or a modified field on the record — and leaves it unchanged when only the template or the CSS changed.
Splitting a sitemap is required above 50,000 URLs, but the more useful reason to split is observability. Separate sitemaps per content type — posts, categories, products, docs — mean Search Console's coverage report tells you which section has an indexing problem instead of giving you one blended number. On a large site this turns a vague "60% indexed" into "the product pages are fine, the tag archives are not", which is an actionable finding.
Image and video extensions still exist and still work, and video sitemaps remain genuinely useful because they carry metadata (duration, thumbnail, content location) that is hard to express otherwise. News sitemaps remain a distinct format with a 48-hour window and a 1,000-URL cap. The hreflang annotations in sitemaps are a solid alternative to link tags for large multilingual sites, since they keep the mapping in one file rather than scattered across thousands of pages.
lastmod from content modification, never from build time, in W3C datetime format.priority and changefreq.Content-Type: application/xml.Sitemap: line into robots.txt as part of the same build.After each deploy, fetch every URL in the sitemap with a HEAD request and assert a 200. On a 5,000-URL site that takes a couple of minutes with modest concurrency and catches redirects and 404s before a crawler does. It is a better use of pipeline time than pinging an endpoint that no longer exists.