Accessibility
- Color Safe
- Tool to help designers create accessible color palettes
- Colorblind Filter
- Display web pages with colorblind filters applied
- Contrast Ratio
- Compare colors to determine their contrast ratio
- Google Mobile-Friendly Test
- Tests a variety of factors for mobile accessibility
- WAVE Web Accessibility Evaluation Tool
- Check for ADA and WCAG compliance issues
- WebAIM Contrast Checker
- Compare any two colors to check their contrast for readability
- WCAG Contrast Checker
- Another contrast checking tool, from WCAG
- W3C Internationalization Checker
- Check for internationalization support
- W3C Link Checker
- Find broken links
Validators
- W3C Spell Checker
- Find misspelled words
SEO / Performance
- Google Analytics
- Extensive site usage reporting (requires proper site configuration)
- Google PageSpeed Insights
- Tests page loading and rendering times and suggests improvements.
- Google Search Console
- Formerly Google Webmaster Tools (requires site ownership validation)
- Neil Patel SEO Analyzer
- A simple, general-purpose SEO reporting tool
General Links
- W3C Developer Tools
- W3C’s full suite of site checking tools