Google’s Gary Illyes confirmed that Google does indeed check to see if an XML sitemap has a change in it before reprocessing the XML sitemap file.

The reason Google does this is because it doesn’t want to waste resources parsing and processing a file that is not changed from the last time that file was parsed and processed.

This question came up at the 5:33 mark in the SEO office hours.

Here is the video embed:

The first point is somewhat obvious, I mean, it just makes computing sense.

That last point is not really new either but it is a good thing Gary mentioned it. Removing URLs from your XML sitemap won’t 100% result in that URL being removed.

Forum discussion at Twitter.