About Heron Tools
Heron Tools is a collection of browser-based utilities for the calculations, conversions and generators that come up in everyday work and hobbies โ with no sign-up and nothing to install. There are currently 500 tools, available in Japanese and English.
What this site is for
The priority is that a tool is usable the moment you need it, without extra steps. In practice that means three things across every tool: no account required, no app to install, and an answer as soon as you enter your numbers. The site carries advertising, but not in positions that get in the way of using a tool. Each tool is also deliberately narrow in scope. A small page that does one calculation and can be reached directly from a search tends to be faster for the person looking than a single do-everything tool.
How the tools are built
Every tool is implemented as JavaScript that runs in your browser, with no code that sends what you enter to a server. Where the browser already provides a capability, the tool uses it: the Canvas API for image work, the Web Crypto API for anything cryptographic. The site itself is a static site built with Next.js, serving pre-generated HTML, so no server-side processing is involved in running a tool.
How results are verified
Tools based on a formula or a published standard are checked against known reference values after implementation. Where a specification publishes official test vectors, the implementation is compared against them โ RFC 6238 for TOTP, RFC 4226 for HOTP, RFC 4648 for Base32 and RFC 4122 for UUID v5, among others. Physics and maths tools use the standard published formulas, and their behaviour at boundary conditions (leap years, division by zero, negative inputs) is checked as well. Even so, please treat results here as estimates. For anything requiring professional judgement โ medical, tax, legal or financial matters โ always confirm with a qualified professional or an official source. We cannot accept liability for losses arising from use of these results. If you spot an incorrect result, please tell us through the contact form. We check every report and fix what is wrong.
How your data is handled
Values you type in, and images or files you open, are not transmitted to or stored on our servers. All processing happens inside your own browser. That means you can use these tools on material you would hesitate to hand to an online service, such as work configuration values or personal photographs. Once a page has loaded, most tools continue to work even with the network disconnected. We do use cookies from Google Analytics and Google AdSense for traffic analysis and advertising. See the privacy policy for details.
Site operator
Operator: niherattyo This site is planned, built and run by one person. It is not a company, and is not affiliated with any organisation. Please get in touch through the contact form below. Reports of bugs or incorrect results are checked and fixed, with a correction noted on the page where appropriate. Site: Heron Tools URL: https://heron-tools.com
Get in touch
For bugs, incorrect results, corrections to anything published here, or requests for new tools, please use the contact form. Every message is read.