SimilarWeb is a digital market intelligence platform mostly focused on websites.

Down For Everyone Or Just Me enables users to check whether a specific website is inaccessible for everyone or only for them.

Custodee is a website monitoring service.

Xenu, or Xenus Link Sleuth, is a computer program that checks websites for broken hyperlinks

DareBoost is SaaS tool allows you to analyze and monitor websites, producing customized reports on web performance and quality.