Screaming Frog SEO Spider - The Screaming Frog SEO Spider is a small desktop program (PC or Mac) which crawls websites’ links...

Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting

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.

WebGazer - Monitor your website's availability with WebGazer, review its performance and get instant notifications when your website goes down. No installation required and free plan available.

SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.

Checkify - Super minimal, simple and inexpensive 24/7 uptime monitoring