How we build and test our tools

A free tool is only worth using if its answer is right. This page explains what every tool on ÆON Toolhub goes through before it is published, and what we do when one of them turns out to be wrong.

1. The logic is tested before the tool has a screen

The part of a tool that calculates, converts or generates is written first as plain code and run against a batch of cases: normal input, empty input, invalid input, the smallest and largest values, and the awkward cases of that subject. Only when every case passes is the same code moved into the page.

This step exists because it keeps catching real mistakes, for example:

• a random number generator that froze the browser tab when asked for numbers above 2³²;
• a percentage calculator that returned zero for 50% of a very small number;
• a color-blindness simulation that showed red as salmon because one value was copied wrong.

None of them reached the live site.

2. Results are checked against the source, not against other tools

When a tool follows a standard, such as a file format, an ID scheme or a unit definition, the standard is the reference, and the page names it where it matters. Copying another website’s output would copy its mistakes too.

3. Every tool is used in English and in a translated page

Many visitors read the site through their browser’s automatic translation. Translation rewrites the page while it runs, and that can silently break a tool. So each tool is tested twice: as written, and with a simulated translation, clicking every button, menu and switch. A tool that breaks when translated is not published. Your own text, code and results are marked so that translation leaves them alone.

4. It has to work on a phone

Each tool is checked on a narrow phone screen with the longest realistic input, to make sure nothing spills off the side of the page. The tool also has to fit the first screen, so it is the first thing you see, not something you scroll to find.

5. It has to be fast

Each page loads only the code of its own tool, never the code of the others, within a size budget per page. Heavy work, like compressing images or generating large files, runs in the background so the page stays responsive.

6. Your data stays on your device

The tools run in your browser. What you type or upload is processed on your device and is not sent to us. The one exception is live voice input (the teleprompter’s voice mode and live dictation): it uses your browser’s own speech recognition, which some browsers run on the device and others send to the browser maker’s servers. Those tools say so on their page. An account is optional and only stores your favorites and reviews. The Privacy Policy has the details.

7. Every page says what the tool does not do

Each tool page has a section on its limits and why they exist. A tool that promises more than it delivers wastes your time, and an honest limit is more useful than a vague claim.

When something is wrong

If a result looks wrong, tell us through the contact page with the tool, what you entered and what you expected. We check it, fix it if it is a mistake, add the case to that tool’s tests so it cannot come back, and update the date at the bottom of the page.

More about the project, and why it exists, is on the About page.