seonaut.org
SEOnaut is an open source SEO auditing and reporting tool. It crawls websites and checks for broken links, redirects, duplicated or missing meta tags, heading issues, hreflang problems and missing image alt attributes. The tool can be configured to crawl subdomains or sitemaps, follow nofollow links, check external links and access password-protected sites via HTTP Basic Authentication. It can also create WACZ archives of a site.