--- title: Free Sitemap Index Generator slug: sitemap-index-generator last_reviewed: 2026-08-09 author: editorial source: LemAudit Free Tools --- ## Intro A sitemap index is a sitemap that lists other sitemaps. You need one as soon as your site outgrows a single file, and most sites reach that point sooner than their owners expect. Google caps one sitemap at 50,000 URLs or 50MB uncompressed, whichever comes first. A store with 12,000 products, 4,000 variant pages and a blog will hit the size cap long before the URL cap, because product entries carry image and video tags that make each line long. There is a second reason to split, and it matters more than the caps. Search Console reports coverage per sitemap. If every URL on your site sits in one file, the report tells you that 8,000 of 20,000 URLs are indexed and nothing else. Split the same URLs into `sitemap-products.xml`, `sitemap-blog.xml` and `sitemap-pages.xml`, and the same report tells you products are 95% indexed while the blog is at 12%. That is a diagnosis rather than a number. The shards cost nothing to create and they turn a vague metric into a specific one. This generator builds the index file. Paste one child sitemap URL per line, optionally with a real last-modified date, and it returns a valid `sitemapindex` document. Everything runs in your browser; no URL you type is sent anywhere. ## What the tool checks Four rules break sitemap index files in practice, and the generator flags all four as you type. **Absolute URLs only.** Relative paths are invalid in a sitemap index. Every `loc` must be a full URL with a scheme. This is the single most common reason a hand-written index gets rejected. **One host.** A sitemap index may only point at sitemaps on the same host as the index itself. Cross-host references are ignored unless you have verified both hosts in Search Console and set up cross-submission deliberately. If you list a mix of `www` and apex URLs, half your file quietly does nothing. **The 50,000 cap applies to the index too.** An index may list at most 50,000 child sitemaps. Very large publishers nest a second level of index files, which Google accepts. **Dates must be W3C format.** `2026-08-01` is valid. `01/08/2026` is not, and an invalid date makes Google discard the whole `lastmod` element for that entry. ## The lastmod trap The generator lets you omit `lastmod` entirely, and for many sites that is the right choice. `lastmod` is meant to record when the content of a sitemap's URLs last changed in a way that matters. What most build pipelines do instead is stamp today's date on every entry at deploy time. Google has been explicit about the consequence: when every date in a file moves in lockstep on every deploy, the signal carries no information and gets ignored. Worse, once a site has trained Google to distrust its dates, an accurate date later on is discounted as well. So supply a date when you have a real one, from a content timestamp in your database or CMS. Leave it out when your only candidate is the build clock. A file with no `lastmod` is treated as unknown, which is honest and costs you nothing. A file full of fabricated dates is treated as noise. ## Submitting the index Submit the index file, not the shards. In Search Console, go to Sitemaps and add the index URL. Google discovers every child from it and reports each one separately. Then add one line to `robots.txt`: ```text Sitemap: https://example.com/sitemap.xml ``` That line is how every other crawler — Bing, and the AI crawlers that now matter for citation traffic — finds the file, since most of them have no submission interface at all. ## FAQ ### How many URLs should each child sitemap hold? Anything up to 50,000, but split by content type rather than by count where you can. Grouping by type is what makes the coverage report useful. If one type still exceeds the cap, number the shards: `sitemap-products-1.xml`, `sitemap-products-2.xml`. ### Can a sitemap index point at another sitemap index? Google accepts nested index files, though the specification does not describe the case. Very few sites are large enough to need it. If you are considering it, first check whether your shards are grouped sensibly, because most nesting is a symptom of poor grouping. ### Do I need to resubmit after adding a shard? No. Google re-fetches the index on its own schedule and picks up new children. Resubmitting does nudge it, which is worth doing after a large launch or a site migration. ### Should the index list gzipped sitemaps? Yes, if you serve them. Both `.xml` and `.xml.gz` are valid, and gzip is worth it for large files. Make sure the server sends the correct `Content-Encoding` header, or the crawler receives a file it cannot parse. ### Does a sitemap guarantee indexing? No. A sitemap is a discovery aid, not an instruction. It helps Google find URLs it might otherwise reach slowly or not at all. Whether those URLs get indexed depends on their quality, their internal links and the crawl budget your site earns. A page that only a sitemap links to is usually a page nothing else on your site considers important. ### What about image and video sitemaps? They are child sitemaps like any other and belong in the index. For video specifically, the extra elements have their own rules; our [video sitemap generator](/tools/video-sitemap-generator) handles those.