# Sitemap discovery

Canonical HTML: /atlas/sitemap-discovery
Atlas version: atlas-2026-07-28-v1
Category: Discovery and crawl frontiers

## Definition

An XML sitemap is a canonical inventory of URLs a site would like crawlers to know about.

## How it works

Crawlers may fetch the sitemap from robots.txt, a remembered location, or a webmaster tool. The sitemap is a hint: inclusion does not guarantee fetching or indexing.

## How to validate it

Use absolute canonical URLs, accurate last-modified dates, and a cohort that has no other discovery route; observe sitemap and page requests as separate events.

## Common failure

Listing duplicates, redirects, blocked URLs, and non-canonical variants creates ambiguous signals and spends crawl attention on low-value addresses.

## Related topics

- [Orphan pages](/atlas/orphan-pages)
- [Seed URLs](/atlas/seed-urls)