About My Toolbox
Free, privacy-first browser tools for developers and professionals. No data leaves your device.
Why This Exists
My Toolbox started as a personal frustration. Every time I needed to decode a Base64 string or format a chunk of JSON, I'd land on a site that either required signup, showed intrusive ads, or worst of all, sent my data to their servers. When you're working with production JWT tokens or corporate config files, that's not acceptable.
So I built the tools I wanted to use myself. The core principle hasn't changed since day one: every computation runs in your browser via JavaScript. The Vercel edge servers that host this site only serve static HTML, CSS, and JS files. After the page loads, zero network requests are made with your input data. You can verify this by opening DevTools > Network tab while using any tool.
How Client-Side Processing Works
Every tool on this site is a React component that processes data entirely within your browser's JavaScript runtime. Here's what this means in practice:
- JSON Formatter uses the browser's native
JSON.parse()andJSON.stringify()methods for validation and formatting. - Hash Generator uses the Web Crypto API (
crypto.subtle.digest()) for SHA-256, SHA-384, and SHA-512 computation. - Base64 Encoder uses
btoa()/atob()with a TextEncoder/TextDecoder wrapper for UTF-8 support. - Image Compressor uses the Canvas API to re-encode images at lower quality, never uploading the original file.
- Financial Calculators implement standard amortization and compound interest formulas in plain JavaScript math operations.
The only outbound requests this site makes are for ad delivery (Google AdSense) and anonymous page view analytics. Neither has access to the data you type into tools.
What We Offer
36+ free tools across multiple categories, available in 5 languages:
Developer Tools
JSON formatter (RFC 8259 compliant validation), Base64 encoder (RFC 4648), URL encoder (RFC 3986), SHA/MD5 hash generator (Web Crypto API, FIPS PUB 180-4), UUID v4/v7 generator (RFC 4122/RFC 9562), regex tester, diff checker, and more.
Financial Calculators
Mortgage, loan, and amortization calculators using the standard amortization formula M = P[r(1+r)n]/[(1+r)n-1]. Compound interest calculator using A = P(1+r/n)nt. Currency converter with live exchange rates.
Converters & Utilities
Unit converter, color picker (HEX/RGB/HSL), QR code generator, image resizer, image compressor, timezone converter, and timestamp converter (Unix epoch to ISO 8601).
Health & Math Tools
BMI calculator (WHO classification, 2000), calorie/TDEE calculator (Mifflin-St Jeor equation, 1990), word counter, scientific calculator, percentage calculator, and date calculator.
Calculation Standards & Data Sources
For tools that produce numerical results, we use published, peer-reviewed formulas and openly documented standards. Here's what powers the math behind each category:
Financial Calculators
All loan, mortgage, and amortization tools use the standard fixed-rate amortization formula (M = P[r(1+r)n]/[(1+r)n-1]), the same formula used by US banks and compliant with Truth in Lending Act (TILA) disclosure requirements. Compound interest uses the standard formula A = P(1 + r/n)nt as documented in any corporate finance textbook.
Health Calculators
BMI classification follows WHO Global Database on Body Mass Index (2000) with adjusted thresholds for Asian populations per the WHO Expert Consultation (2004). Calorie/TDEE estimation uses the Mifflin-St Jeor equation (1990), recommended by the Academy of Nutrition and Dietetics as the most accurate prediction equation for healthy adults.
Developer Tools
JSON validation follows RFC 8259 (The JavaScript Object Notation Data Interchange Format, 2017). Base64 encoding follows RFC 4648 (The Base16, Base32, and Base64 Data Encodings). Hash generation uses the browser's native Web Crypto API implementing SHA algorithms per NIST FIPS PUB 180-4. UUID generation follows RFC 4122 (v4) and RFC 9562 (v7, 2024).
Important Disclaimer
Financial tools: Results are mathematical estimates based on the inputs you provide. They do not constitute financial advice. Actual loan terms, rates, and costs vary by lender, creditworthiness, and market conditions. Consult a licensed financial advisor before making major financial decisions.
Health tools: BMI and calorie calculations provide general estimates only. They are not a medical diagnosis and should not replace professional medical advice. Individual health depends on many factors beyond BMI or caloric intake. Consult a healthcare provider for personalized guidance.
Our Values
Privacy First
All data processing happens in your browser via JavaScript. We never receive, store, transmit, or access your input data. No cookies track your tool usage. Verify in DevTools anytime.
Fast & Free
No signup required. No rate limits. No premium tiers. All tools are completely free. We'll keep them that way.
Multilingual
Available in 5 languages (English, Chinese, Japanese, Spanish, German) with localized content, not just translated interfaces.
Transparent
We document calculation formulas, cite standards, and explain limitations. If a tool has edge cases or accuracy limits, we tell you upfront.
Technical Stack
Built with Next.js 15 (App Router), React 19, TypeScript, and Tailwind CSS. Hosted on Vercel Edge Network for global low-latency delivery. All tools are server-side rendered for SEO, then hydrated as client components for interactivity. No user data touches our servers during tool operation.
How We're Supported
My Toolbox is free to use and supported by non-intrusive advertising through Google AdSense. This allows us to keep all tools free while covering hosting and development costs. We limit ad placements to avoid interfering with your workflow.
Contact
Have questions, feedback, or suggestions for new tools? Reach out.
Email: hello@tools.aiappbox.tech