SiteInspector is a free, open-source tool that helps to find spelling errors, grammatical errors, and broken links on websites. The tool can be deployed using Docker or Heroku in less than 5 minutes.
LinkChecker - LinkChecker is a free, GPL licensed website validator.
Website Checker Tech - WebsiteChecker.Tech is SaaS tool that detects SEO and availability issues of your website, making it easier for you to fix them.
Pulno - SEO Audit and Website Analysis. Pull up your SEO.
SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
Dead Link Checker - Check for broken links on any website
Sitechecker - All-in-one SEO platform including rank tracker, website SEO audit tool and website changes monitoring. Detailed reports by 100+ parameters with how-to-fix guides.