About Mavis Tools

Mavis Tools is a set of 242 small, free web tools: word counters, loan and mortgage calculators, JSON formatters, password generators, image resizers and more. Each one does a single job and gives you the answer on the first screen, without a sign-up wall or a pop-up asking for your email.

Who builds it

I'm Divyansh Shukla, a developer and the founder of Mavis Tools. I design, write and test every tool on this site myself. The project started from a simple frustration: the top search results for everyday tasks like "count words" or "format JSON" were slow, buried under ads, or quietly uploading whatever you pasted to a server.

So the rule here is the opposite. A tool should load fast on a cheap phone, work with no account, and keep your data on your device.

Why everything runs in your browser

Every tool on Mavis Tools runs entirely in your browser with JavaScript. The text you type, the numbers you enter and the files you open are processed on your own device and are not uploaded to us. That matters when you are pasting an API token, a salary, a client's draft or a private photo. You can check it yourself: load a tool, turn off Wi-Fi, and it still works.

There are no accounts and no saved history. The site uses Google AdSense to pay for itself, which is covered in the privacy policy.

How tools are built and checked

• Standard formulas, shown on the page. Calculators use published, standard formulas (for example the amortization formula for loans, or Mifflin-St Jeor for BMR), and each page explains the formula so you can check the result instead of trusting a black box.
• Worked examples. Before a tool ships, I run it against hand-worked examples and edge cases (zero, negative, very large, empty input) and compare the results with at least one other trusted source.
• Native browser engines. Developer tools use the browser's own parsers (JSON, RegExp, URL, Web Crypto), so what you see matches what your code will see.
• Real devices. Every page is checked on a phone-width screen and a desktop, in light and dark mode, for keyboard access and readable contrast.
• Dated updates. Each tool page shows when it was last updated, and I fix reported errors as soon as I can confirm them.

Results are estimates for planning. For money, health or legal decisions, confirm the final numbers with a qualified professional.

Found a mistake or want a tool?

Corrections, bug reports and tool requests go straight to me at [email protected]. You can also use the contact page. If you spot a wrong result, include the inputs you used and what you expected, and I'll check it against the formula.