About Toolcin
368 browser tools, built and checked one at a time. This page explains how, and what is deliberately missing.
What this site is
Toolcin is an independent project: a set of static pages, one per tool, that do their work in your browser. There is no account system, no upload endpoint and no database. That is a technical fact, not a marketing line — the repository contains no server code at all.
How a tool gets built
Every tool is written in plain JavaScript against the browser APIs it needs. Where a third-party library is used, it is named on the page and in the source: pdf-lib and pdf.js for PDF work, SheetJS for spreadsheets, JSZip for archives, jsQR for scanning, ffmpeg compiled to WebAssembly for media, libheif for HEIC decoding, Tesseract for OCR.
Nothing is embedded from another tool site, and no tool is a screenshot or an iframe of somebody else's service.
How it is tested
Each tool is run with a known input and the output is checked, not eyeballed. Conversions are verified against the stated factor, calculators against the formula, and file tools by re-reading the file that comes out:
- Hash functions checked against published test vectors for MD5, SHA-1, SHA-256 and SHA-512.
- Loan and amortisation arithmetic checked against an independent calculation — the monthly payment on 2,000,000 at 12% over 10 years is 28,694.19, and month one splits 20,000.00 interest to 8,694.19 principal.
- PDF output checked by parsing the produced file and confirming the page count and the extracted text.
- Archives checked by unzipping the result and comparing the contents with the input.
- Unit pairs checked factor by factor against the definition each one is built on.
Where a tool cannot be verified in an automated test — the screen recorder needs a real display picker, for example — the page says so rather than claiming it was proven.
What is deliberately not here
No platform downloaders, no tools that would need someone else's paid data set, no AI features that would require a hidden API key, and no number invented to look impressive. If a result is an estimate, the page calls it an estimate.
Health and money calculators
The BMI, BMR, body-fat, calorie, due-date, loan, tax and zakat pages use published formulas: WHO adult cut-offs, the Mifflin–St Jeor equation, the US Navy tape method, Naegele's rule, the standard amortising loan formula and the income-tax slabs coded in the page. Each page states the formula and its limits. They are calculators, not advice, and no clinician or adviser has reviewed them.
Corrections
If a tool gives a wrong answer, the fastest route to a fix is an email with the tool name, the input you used and the output you saw. Corrections are treated as bugs and are prioritised over new features. Contact details are on the contact page.
Funding
The site is free, has no ads and no paid tier. It is a small independent project rather than a business with a support desk.