A sitemap is a list of the URLs on your site that you would like a search engine to know about. It is genuinely useful, and it is also the SEO artefact people have the most superstitions about — including two fields this tool generates that Google throws away on arrival.
Google ignores priority and changefreq. Both of them.
This is not a rumour or an inference from ranking data. Google said it publicly and has repeated it: priority and changefreq are not used. They are read and discarded.
The reason is the same one that killed the meta keywords tag. Both fields ask a site owner to declare something about their own pages, and every site owner has the same incentive — set everything to priority 1.0 and changefreq hourly. When every page on the web claims to be maximum priority and updated constantly, the field carries no information, and a signal that carries no information gets dropped. It took about a decade for that to become official, and the fields are still in the spec, still generated by every tool, and still filled in earnestly by people who believe they are doing something.
They are generated here because the format defines them and their absence confuses people more than their presence. Setting them costs nothing and achieves nothing. If you have been carefully tuning priority values, that time is recoverable and better spent elsewhere.
lastmod is used — but only if you are honest
The one optional field that survives is lastmod, and Google has been explicit about the condition: it is used when it is consistently accurate, and ignored entirely when it is not.
The failure mode is a site that stamps every URL with today's date on every regeneration. It looks like an entire site rewritten daily, which is not credible, and Google responds by disregarding lastmod for that site altogether. You have not gained faster recrawls; you have lost a working signal.
So lastmod should reflect when the content meaningfully changed. Not when the template was touched, not when the build ran, not when a footer year rolled over. If your generator cannot tell the difference, leaving lastmod out is strictly better than filling it with a lie — an absent field is neutral, a dishonest one poisons the well.
A sitemap does not get you indexed
This is the expectation worth resetting. A sitemap helps a crawler discover URLs. It does not oblige anyone to crawl them, and it certainly does not oblige anyone to index them. Submitting a page and watching it stay out of the index is not a broken sitemap; it is Google deciding the page is not worth including.
Where a sitemap genuinely earns its place is discovery: pages that are barely linked from anywhere, a large site where crawling every path takes weeks, a new site with no inbound links, or content that changes faster than a crawler would notice on its own. If your pages are well linked from your own navigation, a sitemap adds very little — the crawler was going to find them.
Which means the useful thing a sitemap gives you is not traffic. It is the coverage report in Search Console: submitting a list of what you think should be indexed lets you see the gap between that and what actually is. That gap is where the real problem usually is.
The limits, and what to do about them
A single sitemap holds at most 50,000 URLs and 50 MB uncompressed. Past either, you split into several files and point at them with a sitemap index — a sitemap of sitemaps, which every engine supports and which is the normal arrangement for any site of size.
One rule catches people: only include URLs you actually want indexed. A sitemap listing pages that are noindexed, canonicalised elsewhere, redirecting, or returning 404 sends contradictory instructions, and Search Console will report it as an error rather than quietly ignoring it. The sitemap should agree with the rest of your site — it is a statement of intent, and it is worth keeping true.
Common questions
Is anything sent to a server?
No. This tool is marked "client": the XML is assembled in your browser tab from the URLs you paste. Nothing is transmitted.
Should I bother setting priority?
No. Google discards it, and no other major engine has ever given evidence of using it either. Leave the default. Any time spent deciding whether a page is 0.8 or 0.6 is time spent on a field that goes in a bin.
Do I need a sitemap at all?
For a small, well-linked site, honestly not much — a crawler following your navigation will find everything. It becomes worthwhile as sites get large, as pages get buried, or when you want the Search Console coverage report to tell you which of your pages are not indexed. That report is the real return on the effort.
Where do I put it, and how does Google find it?
Anywhere on your domain, though the root is the convention. Two ways to announce it: a Sitemap: line in robots.txt, which every engine reads, and submitting it in Search Console, which is how you get the coverage report. Do both — they cost one line and one click.
How often should I regenerate it?
When URLs are added or removed, which for most sites means as part of the build. What matters is that it stays accurate — a sitemap listing pages that no longer exist is worse than no sitemap, because it is actively wrong. Regenerating on a timer without checking is how sitemaps drift out of sync with the site they describe.