How do I convert an HTML sitemap to CSV?

An HTML sitemap is a normal webpage that lists internal links — usually at /sitemap or /sitemap.html — rather than the machine-readable XML at /sitemap.xml. To convert it to CSV, parse the page's HTML, pull every <a href> value, resolve relative URLs against the page URL, dedupe, and write to CSV. Don't try this in Excel — its XML importer won't parse HTML. The xmlsitemapmaker.com HTML sitemap converter handles all of this in one step: paste the URL of the HTML sitemap, get back a CSV of every internal link, fully-qualified and deduplicated. Useful when the site doesn't publish an XML sitemap, or when /sitemap.xml is incorrectly serving an HTML response.