Free Online Developer Tools & Financial Calculators
JSON formatter, Base64 encoder, loan and mortgage calculator, unit converter, and 45 browser tools. Client-side processing, no signup, no data sent to servers.
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What Is AI App Box?
AI App Box is a collection of 45 browser-based utilities built for people who'd rather get things done than hunt for the right app. Every tool runs entirely in your browser — your data never leaves your device, and there's nothing to install or sign up for.
We started this project in 2024 after getting tired of ad-heavy "free" tools that upload your JSON configs or passwords to unknown servers. The result: fast, private utilities that work offline once loaded. No tracking pixels, no email gates, no upsells.
A Note From the Developer
Why I Built This Site
AI App Box is a solo project. I'm an independent developer who builds browser-based utilities in my own time, and I run this site because I got tired of the same trade-off showing up on every online tool: sign up, watch ads with modal popups, or paste your data into a page that quietly logs everything server-side. When you're decoding a production JWT or checking a loan calculation with real numbers, none of those are acceptable.
Every tool here is a plain React component that computes results inside your browser. The static CDN only serves HTML, CSS, and JavaScript files. After a page loads, nothing you type is sent anywhere — you can verify this yourself by opening DevTools > Network while using any tool. Financial and health calculators document the formulas they use (WHO 2000 BMI thresholds, Mifflin-St Jeor for calories, standard amortization for mortgages) so you can double-check the math, not just trust a black box.
I update tools when I find bugs, when users email me about edge cases, and when the underlying standards change. If a tool has a known limitation, it's written in the tool's own page — not hidden in fine print. Feedback is genuinely welcome through the contact page.
Developer Tools
Format JSON with trailing-comma detection, encode Base64 for JWT debugging, generate SHA-256 hashes for file integrity checks, or test regex patterns with real-time highlighting. Built by developers who use these tools daily — so edge cases like 50 MB JSON files and multi-line regex are handled properly.
Financial Calculators
Run mortgage scenarios with extra-payment comparisons, calculate compound interest with the Rule of 72, or convert currencies using mid-market rates. Every calculator shows the formula it uses and lets you export results — no black-box math.
Converters & Utilities
Convert units across 10 categories, pick colors in HEX/RGB/HSL, generate QR codes up to 4,296 characters, or calculate BMI with WHO classification. Each tool is keyboard-accessible and works on mobile without layout shifts.
Why People Use AI App Box
100% Client-Side Processing
Your data stays in your browser. We don't send anything to a server — check the Network tab yourself. No cookies, no analytics, no fingerprinting.
Actually Free, No Catch
No freemium limits, no "sign up to unlock" walls, and no paid tiers. A small number of non-intrusive ads helps cover hosting and development.
Zero Registration Required
Bookmark it, use it, close it. We don't need your email, and we won't ask for it. Ever.
Sub-Second Load Times
Static pages served from a global CDN. Typical first-paint is fast on mobile connections, with no client-side framework hydration blocking your input.