XML Sitemaps: Giving Crawlers a Clean Map of Your Site

A sitemap is a discovery aid. It tells search engines which URLs you consider worth crawling and roughly when each last changed. On a small site with clean internal linking it changes little. On a large site, a new site, or one where useful pages sit 4 clicks from the homepage, it is often the difference between a page being found this week and next quarter. Two properties make a sitemap useful: it is discoverable, and it is honest. Discoverable means it is referenced from robots.txt or submitted directly, and it lives at a stable URL. Honest means every URL in it is one you would want indexed, which is to say canonical, returning 200, and open to crawling. The most common defect is a sitemap generated once and never regenerated, listing URLs that now redirect or 404 while omitting everything published since. The second is a sitemap containing every URL the CMS can produce, including tag archives, paginated duplicates and parameterized variants. Both teach search engines to trust the file less. A healthy sitemap can be found, parses as valid XML, and uses index and child files correctly. Every URL it lists should also agree with your own directives, because a file that nominates blocked, noindexed or non-canonical URLs is arguing with itself, and search engines settle that argument by trusting the file less.

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