XML is the standard format. RSS/Atom feeds and a plain text list of URLs also work; the text format is one URL per line, UTF-8, nothing else.
Submitting
- Search Console, the Sitemaps report. This is the method that gives you feedback: parse errors, discovered URL counts, last read date.
- robots.txt, add a
Sitemap:line with the full absolute URL. Every crawler reads it, not just Google.
The old “ping” URL for notifying search engines of sitemap updates has been retired by Google and no longer does anything.
Sitemap index files
When you exceed the per-file limits, create an index that points at the individual sitemaps. Splitting by content type, products, articles, categories, has a diagnostic benefit: the coverage report then tells you which section has an indexing problem.
Alien Road recommends: split by content type even when you are under the limit. On a shop we worked on, a single 40,000-URL sitemap showed “some pages not indexed” and nothing more. Split into four, the report immediately showed the problem was confined to filtered category URLs, a fifteen-minute diagnosis instead of a day.