Handy tools that run in your browser

84 tools · No installs or sign-ups · Everything runs in your browser

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JPG, PNG or WebP: which to use and how to reduce file size
How JPG, PNG and WebP differ in compression and transparency, which suit photos and logos, why converting may not shrink a file, and how to hit a target size.
Why character count and byte count differ
How characters, code points, UTF-16 code units and bytes differ, with examples of UTF-8 sizes, emoji, legacy encodings and how to tell what a limit counts.
How online tools work without uploading anything
How server-side and in-browser tools differ, and two quick ways to check for yourself that your input isn't sent anywhere, using DevTools and offline mode.
Percent vs percentage points, and common percent mistakes
Three basic percent calculations and percent vs percentage points, in numbers. Also checks common slips: up then down, stacked discounts, reverse percentages.
How much protein do you need if you train?
Where the protein calculator's 'If you train' range of 1.2–2.0 g per kg comes from, how it differs from the recommended intake, and how it is worked out.
What BMI does not tell you
BMI uses only height and weight. Why it cannot see muscle, where fat sits, age or sex, and why waist size is checked too.