A sitemap is a file on your website, usually at yourfirm.co.uk/sitemap.xml, that lists every page you want Google to know about. It is not for humans. It is a delivery note handed to the search engines saying here is everything, in one place.
What it does and does not do
It helps search engines find pages, particularly new ones and ones that are not linked to from many places. Google's own sitemap documentation is clear that it is a hint, not an instruction.
It does not make a page rank. It does not force a page to be indexed. A thin page listed in a sitemap is still a thin page. What it does is remove the excuse that Google never found it.
A worked example
A builder added six new town pages and then wondered for two months why none of them appeared in Google. Nothing on the site linked to them except a small line in the footer, and the sitemap had not been regenerated since the site was built.
Adding them to the sitemap and submitting it in Search Console got them crawled within days. They still had to earn their place after that, but at least they were in the race.
Checking yours
Type your address followed by /sitemap.xml. If you get a wall of addresses, you have one. Read a few and check they are the addresses you expect, on the right domain, with https. Then make sure it is submitted in Google Search Console and that the last read date is recent.
Why it matters for your site
Check these on your own site
- Every page you care about should be in it. Nothing you have hidden or retired should be.
- Submit it once in Search Console, then check the last read date every few months.
- It should regenerate when you add pages. A stale sitemap is a slow crawl.
- Only list the address you actually want indexed, matching your canonical.
- A sitemap gets pages found. It does not get them ranked.
Common questions
Does a small website need a sitemap?
It helps, and it costs nothing. On a small, well linked site Google will usually find everything anyway, but a sitemap removes the doubt and shows you what you have published.
Will a sitemap improve my ranking?
No. It helps pages get found and crawled. Whether they rank depends on the page itself, the links to it and how well it answers the search.