Does a sitemap guarantee my pages get indexed?
No. A sitemap helps search engines discover URLs and understand when they change, but each page is still judged on its own quality. It is most useful for new sites with few external links, large sites, and pages that are hard to reach through navigation.
Should I include every page of my site?
Include only the canonical, indexable pages you want in search results. Leave out redirects, error pages, pages marked noindex, and duplicate URLs with tracking parameters. A sitemap full of URLs that should not be indexed weakens the signal it sends.
Do changefreq and priority matter?
Google has said it ignores both. An accurate lastmod date is the field that helps, and only when it changes because the content changed in a meaningful way. Other search engines may still read changefreq and priority, so including them does no harm.
How do search engines find my sitemap?
Submit it in Google Search Console and Bing Webmaster Tools, and add a "Sitemap: https://example.com/sitemap.xml" line to robots.txt so every crawler can find it without being told.
How large can a sitemap be?
One sitemap file can hold up to 50,000 URLs and be up to 50 MB uncompressed. Larger sites split their URLs across several sitemaps and list them in a sitemap index file, which can then be submitted as a single URL.