The short answer
An XML sitemap is a file that lists the pages you want Google to know about. It helps Google find pages, but it does not make them rank. Most small sites already have one from their CMS; the job is to make sure it lists the right pages and nothing else.
What the file actually is
An XML sitemap is a plain file, usually at an address like yoursite.com/sitemap.xml, that lists the pages on a website you want search engines to crawl. Each entry is a web address, sometimes with the date it last changed. Google reads the file as a set of suggestions about where to look.
A sitemap is not a navigation menu for visitors and it is not a ranking signal. A page listed in it still has to be worth indexing on its own merits. What the file does is remove one reason a good page might be missed: Google not knowing it exists.
Does a small business site need one
Google's own guidance is that a small site with good internal links may be found perfectly well without a sitemap. In practice there is little reason not to have one. WordPress creates a basic sitemap automatically, and most SEO plugins and site builders generate their own.
A sitemap matters more when:
- the site is new and has few links pointing to it from elsewhere
- pages are added often, such as articles or location pages
- some pages are not linked well from the rest of the site
- the site has just moved to a new domain or a new structure
For a five-page site that rarely changes, the sitemap is a small safeguard. For a site publishing every week, it is part of how new pages get found quickly.
What it should and should not contain
A useful sitemap lists the pages you would be happy to see in search results, at their final address. It should not list:
- pages that redirect somewhere else
- pages marked noindex or blocked by robots.txt
- thank-you pages, test pages and internal search results
- duplicate versions of the same page, such as with and without a trailing slash
When a sitemap is full of addresses Google cannot or should not index, it becomes a weaker guide. Search Console will often show these pages under statuses such as Page with redirect or Excluded by noindex tag, which is a clue the sitemap needs tidying. Our answer on what Crawled, currently not indexed means covers another status that often turns up in the same report.
How to check yours
Open the sitemap address in a browser and look through it. Then, in Search Console, go to Sitemaps, submit the address if it is not already there and check that Google reports it as read successfully. Google's sitemap overview covers the format if you need the detail.
Finally, pick a few important pages and make sure they appear in the file. If a key service page is missing, that usually points to a setting in the CMS or plugin rather than a problem with the page itself. If you would rather have someone check the whole picture, an SEO audit starts with exactly this kind of review.