Antigravity Tools：以原生 JavaScript 建立 59 款免費瀏覽器開發工具的心得

I've been quietly building Antigravity Tools — a collection of 59 free, browser-based developer utilities — and today I'm sharing everything I built and learned.

Why vanilla JS? No React, no build step.

The main constraint I set for myself: zero dependencies, zero server, zero telemetry.

When you paste your JWT token into jwt.io, it goes to their server. When you use an online regex tester, your test strings are logged. I built Antigravity Tools so every operation runs inside your browser, using native APIs.

No Node.js backend
No npm packages
No webpack/vite/parcel
No Google Analytics
No cookies

Everything runs on Web Crypto API, Canvas API, Web Audio API, and IndexedDB — all native to modern browsers.

The 8 tool categories

🔐 Security & Auth Tools

JWT Inspector — decode JWT header, payload, and check expiry locally
RSA & ECC Key Generator — generate 2048-bit key pairs via SubtleCrypto
Hash & Password Generator — SHA-256/SHA-512 via Web Crypto
PII Masker — strip emails, credit cards, SSNs, IPs from text
Universal Encoder/Decoder — Base64, URL, Hex, HTML entities, Unicode

🤖 AI & Prompting Tools

AI Token Counter — estimate cost across GPT-4o, Claude 3.5, Gemini 2.0, DeepSeek R1
System Prompt Builder — structure agent instructions with XML tags and tool definitions
AI Text Humanizer — rephrase robotic AI output into natural writing
Prompt Cost Trimmer — compress prompts by 30–50% to reduce API costs

⚡ Dev & Code Tools

JSON Workbench — beautify, validate, convert to TypeScript, Python, Go types
cURL Converter — cURL → JS fetch, Python requests, Go, PHP
Regex Tester — real-time match highlighting with capture group display
Cron Builder — visual cron expression editor with plain-English output
Git Command Helper — build undo/squash/cherry-pick commands visually

Try it

👉 https://antigravitytools.app