Free Online Tools for Everyone
213 calculators, converters, developer utilities and reference lookups. No signup, no downloads, no usage limits — and 196 of them run entirely in your browser, so nothing you type is ever sent to a server.
What this site is
OnlineToolHubs is a collection of single-purpose web tools — the kind of thing you search for once, use for thirty seconds, and close. A percentage worked out, a JSON blob formatted, a PDF split in two, a mortgage total checked before signing something.
Most of them never send your data anywhere. 196 of the 213 run entirely in your browser using JavaScript, which means the document you open, the salary you type and the token you paste stay on your own machine. That is not a marketing line — it is a consequence of how they are built, and it is why there is no account system here to attach data to.
The remainder query public APIs — weather from national meteorological agencies, DNS records, currency rates — and each of those pages names the service it calls and says what happens when it is unavailable.
Start here
A hand-picked starting point — not a popularity ranking, since we do not track you well enough to have one.
- Percentage Calculator — Covers all three percentage problems, including the reverse one people get wrong.
- JSON Formatter & Validator — Formats and validates locally, pointing at the character where parsing failed.
- Merge PDF — Combines PDFs without uploading them to anyone.
- Word Counter — Words, characters, sentences and reading time in one pass.
- QR Code Generator — Generates a real scannable code with adjustable error correction.
- Mortgage Calculator — Shows total interest over the term, not just the monthly payment.
- Image Compressor — Shrinks photos on your own device, with before and after sizes.
- Unit Converter — Length, mass, volume, temperature, area and speed with exact factors.
- Password Generator — Generated in your browser from the platform crypto API, never transmitted.
- TDEE & Calorie Calculator — Mifflin-St Jeor with the activity multiplier explained rather than hidden.
Browse by Category
12 categories, each with an overview of what the tools in it actually do
Why so many of these run in your browser
A tool that processes your data on a server has to receive that data first. For a word counter that hardly matters; for a PDF splitter handling a contract, a JWT decoder handling a live token, or an image tool handling a passport photo, it matters a great deal — and the retention policy governing what happens to that upload is usually several clicks away and rarely reassuring. Building these as client-side tools removes the question rather than answering it. There is no upload, so there is nothing to retain, log or leak. The trade is that processing speed depends on your device rather than our hardware, which for the sizes involved is not a meaningful constraint.
Every tool shows its working
A calculator that returns a number and nothing else cannot be checked, which means you have to trust it. Each page here states the formula it applies, defines the symbols, works through a numeric example with real figures, and cites where the method came from — whether that is a published equation, a standards document or a government dataset. It also states what the tool cannot do. That last part is the one usually left out, and it is often the most useful thing on the page.
What we do not do
There is no account system, so there is nothing to sign up for and no profile to build. We do not ask for location permission, including on the weather tools, which take a city name you type instead. We do not sell data, because for the browser-based tools we never receive any. The site is supported by advertising, which is disclosed in the footer and in the privacy policy along with what that involves. If a tool needs to call an external service to work, its page names the service.
When a tool cannot give you an answer
Free public APIs go down, rate-limit, and occasionally disappear entirely — several that tools like these commonly rely on have shut off without notice. Where that happens, the tools here are built to say so rather than fill the gap with a plausible-looking number. A stored figure is labeled as stored, a rate limit is reported as a rate limit, and a lookup with genuinely no result says that instead of showing a zero. A confident wrong answer is worse than no answer, particularly for anything you are about to act on.
Frequently asked questions
Are these tools really free?
Yes. There is no account, no trial, no paid tier and no usage cap. The site is funded by advertising.
Do I need to create an account?
No, and there is no way to. No tool on the site requires or offers registration.
Is my data uploaded when I use a tool?
For most of them, no — they run entirely in your browser and the data never leaves your device. The ones that query an external service do so because the answer requires a network request, and each of those pages names the service it calls.
Do the tools work on mobile?
Yes. Every page is responsive and works in any current mobile browser. There is no app to install.
Can I use these tools offline?
The browser-based ones keep working once the page has loaded, since the logic ships with the page. Anything that depends on a live API needs a connection.
How accurate are the calculators?
Each one applies a stated published formula and shows its working, so you can verify any result by hand. Where a method has known error margins — body fat estimates, heart rate maximums, elevation models — the page says what they are rather than presenting a figure as exact.
Can I suggest a tool?
Yes. Email contact@onlinetoolhubs.com with what it should do and why it would be useful.