Free online tools that run in your browser

Most online tool sites are built the same way: you upload a file or paste your text, a server somewhere processes it, and a result comes back. That architecture is simple for the operator and unnecessary for you. Modern browsers can parse a megabyte of JSON, run a regular expression or amortise a thirty-year loan without help from anyone.

Every tool here is built on that principle. The calculation happens in the tab you already have open. There is no upload step, no queue, no temporary file sitting on a disk you cannot see, and no round trip adding latency to something that should be instant. It also means the tools keep working when your connection drops.

Accuracy you can check

A calculator that produces a number with no explanation is impossible to trust. Every calculator on this site states the formula it uses and shows a worked example, so you can verify the result by hand or in a spreadsheet. Where a convention is genuinely contested — whether a day count includes both endpoints, whether a month is thirty days or a real calendar month, whether a gigabyte is a billion bytes or 2³⁰ — the page says which choice it made and why.

Built for speed

Pages are pre-rendered as static HTML, so a tool is on screen before any script runs, and there are no web fonts to download. Two third-party scripts do load: the advertising that funds the site, and Google Analytics, which counts page views. Both are loaded asynchronously so neither holds up the page, both set cookies, and the privacy policy explains what each collects and how to opt out. Neither can see what you type into a tool — that never leaves the page.

Privacy by architecture, not by policy

A privacy policy is a promise. Client-side processing is a property of the software. When you paste a production API response into the JSON formatter or a real salary into the loan calculator, that data never leaves your machine — not because we choose not to store it, but because there is nothing to store. Read the privacy policy for the full detail, including what our advertising partner does and does not see.

Made to grow

The catalogue is defined in one place, with each tool carrying its own description, category, related links and page copy. That is why new tools appear complete rather than as bare calculators with a headline — and why the ones still being built are marked as such instead of shipping as empty pages.