Dr. Link Check - Broken link checker with malware and parked domain detection

RainforestQA - Insanely simple testing. Create tests for your website in plain English, then run them across all major browsers with a single click. Powered by human intelligence

LinkChecker - LinkChecker is a free, GPL licensed website validator.

Bitrise - Tens of thousands of agencies, startups and enterprise companies with mobile apps - including Runkeeper, Grindr, Duolingo and more - use Bitrise to automate their way to increased productivity & speed

SiteInspector - Catch spelling/grammar errors and broken links on websites.

Cypress.io - Slow, difficult and unreliable testing for anything that runs in a browser. Install Cypress in seconds and take the pain out of front-end testing.