The sitemap protocol sets two hard limits on a single file. Stay inside them and search engines will read your sitemap without complaint; cross them and the file may be rejected or only partly read.
Maximum URLs in one sitemap file.
Maximum uncompressed file size.
What to do when you outgrow them
Whichever limit you hit first, the answer is the same: split your URLs across multiple sitemap files and reference them all from a sitemap index file. A busy site with long URLs often hits the 50 MB size ceiling well before the 50,000-URL count, so watch both.
Gzip is allowed — and encouraged
Search engines accept gzip-compressed sitemaps (sitemap.xml.gz),
which dramatically reduces transfer size and speeds up fetching. Note that the 50 MB limit applies to the
uncompressed XML, not the compressed download — so compression does not let you pack in more URLs,
it just makes delivery cheaper.
This tool handles it for you
When a crawl produces more URLs than fit in one file, the generator splits them automatically and writes a sitemap index — plus a gzipped copy — so you never have to track the limits by hand.
Keep reading