About OneUtil
OneUtil is 28 small developer tools under one roof — calculators, converters, encoders, a PDF toolkit, a diagram studio — that all run entirely inside your browser.
Why it works this way
Most utilities like these are web forms that post your input to a server. That is fine for a unit conversion and genuinely risky for a contract, a JWT, or a .env file. Every tool here is JavaScript running on your own machine: there is no backend to receive your data, no account, and no upload step. After the first visit the whole site is cached, so it keeps working with no connection at all.
The one deliberate exception is the currency converter, which has to fetch exchange rates. It sends the currency pair and nothing else. The privacy page sets out exactly what does and does not leave your device.
How it’s paid for
It’s free, and it’s supported by ads. That keeps it open to everyone with no sign-up and no paywall, and it is why the site shows advertising from Google. Ads are placed under a tool’s working area and between sections — never inside the tool itself, and never anywhere they could be mistaken for a button you meant to press.
Who makes it
A personal project, built and maintained by one person. Bugs, wrong answers and missing tools are all worth reporting — if a tool gives you an incorrect result, I would genuinely like to know.
Contact
Email hello@oneutil.dev for bug reports, corrections, privacy questions or anything else.