How we test our tools

1. We run every tool in a real browser

Each tool is opened in a real browser and used the way a visitor would use it: files are added, options are changed and the result is downloaded. We do not rely only on reading the code.

2. We check results against known values

For tools that produce a number or a file, we compare the output with something we know is right.

• Calculators are checked against independent calculations and hand-worked examples. For the loan calculator we confirm that the principal repayments add up to exactly the loan amount and that the last balance is zero.
• File converters are checked by opening the result and reading it back: image sizes and colours, the pages and order of a PDF, the files inside a ZIP, the text inside a QR code.
• Encoders such as Base64 are compared with a reference encoder and must return the original text when decoded again.
• Date and time tools are tested at the awkward points: month ends, leap years and 29 February.

3. We try the edge cases

We test empty input, wrong input, very large input, text in other languages (Urdu, Hindi, Arabic and emoji) and files that are damaged or password protected. A tool should say clearly what is wrong, not fail silently.

4. We say what a tool cannot do

Every tool page has a questions section that states its limits, such as the biggest file size or what a result does not include. Health calculators say that they give general guidance and are not medical advice. The AI tools say that they make a good estimate, not a perfect one.

5. We fix mistakes in the open

If a reader or our own testing finds an error, we fix it, test it again and update the page. If you think a result is wrong, please tell us which tool, what you entered and what you expected.

What our testing does not cover

We cannot test every file, device and browser. A recent version of Chrome, Edge or Firefox gives the best results. Large files may be slow on older phones. Spreadsheet, OCR and AI results should still be checked by you before you depend on them.

Last updated 11 November 2026.