Sitemap Split/Merger Tool

How this tool computes its result

One tool, two modes via a dropdown. Split mode fetches one sitemap's URLs (capped at 200,000), chunks them into fixed-size groups (500-50,000 per file, user-selectable), and -- only when the split produces more than one file -- also builds a sitemap-index XML referencing each split file by name, optionally prefixed with a supplied base URL. Merge mode fetches multiple sitemap URLs sequentially (one per line, not in parallel), concatenates every URL, deduplicates via a Set, and emits one merged urlset file, flagging client-side (not enforced) if the merged total exceeds 50,000 URLs.

Worked example

Splitting a 12,400-URL sitemap at 5,000 URLs per file produces 3 files (5,000 / 5,000 / 2,400) plus one sitemap-index.xml. Splitting a 3,000-URL sitemap at the same 5,000-per-file setting produces only 1 output file and no index file at all, since the more-than-one-file condition is never met.

When not to use this tool

Merge mode fetches each source sitemap sequentially inside the browser tab, not in parallel or server-batched, so merging several large sitemaps at once can be noticeably slow and remains bounded by the same 200,000-URL-per-source cap as the other sitemap tools.

Common mistakes

• - Expecting a sitemap-index file even when a split only produces one output file -- the index is only generated when the result is more than one file, by design.
• - Merging sitemaps that share duplicate URLs and expecting the per-file counts to sum to the pre-merge total -- deduplication happens across all sources combined, so the final count can be lower than the sum of individual source counts.
• - Leaving "Base URL for index sitemap" blank when the split files won't be hosted at the source sitemap's own origin -- without it, the index file falls back to that origin, which may not be where you're about to upload the split files.

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