A collection of 1,680+ free browser-based tools that run entirely client-side. Your data never leaves your device. • Finance — mortgage, budget, debt payoff, retirement, tax calculators • Health — BMI, calories, sleep, reaction time, burnout test • Developer — JSON formatter, regex tester, JWT decoder, cron generator • Design — background remover, image compressor, favicon generator • AI — grammar checker, article summarizer, cover letter helper • 40+ categories covering 20+ countries