I built 59 free browser-based dev tools in vanilla JS — here's what I learned

I have recently completed Antigravity Tools, a collection of 59 free, browser-based developer utilities. The project aimed to build these tools using vanilla JavaScript, without relying on frameworks, build processes, or external dependencies. My primary goal was to ensure that every operation occurred within the browser, utilizing only native APIs such as the Web Crypto API, Canvas API, Web Audio API, and IndexedDB.

Unlike other online tools that transmit user data to external servers, Antigravity Tools processes everything locally. For instance, when you paste a JWT token into the JWT Inspector, it analyzes the token directly in your browser, rather than sending it to jwt.io's server. Similarly, the Universal Encoder/Decoder strips sensitive information like emails, credit card numbers, and IP addresses from text without any server-side processing.

The project comprises eight main categories of tools:

1. Security and Authentication tools

2. AI and Prompting tools

3. Dev and Code tools

4. JSON Workbench

5. cURL Converter

6. Regex Tester

7. Cron Builder

8. Git Command Helper

Each tool serves a specific purpose, aiming to reduce reliance on online services and enhance user privacy. For example, the AI Token Counter estimates the cost of using popular AI models like GPT-4o, Claude 3.5, Gemini 2.0, and DeepSeek R1. The System Prompt Builder structures agent instructions using XML tags and tool definitions, while the AI Text Humanizer rephrases robotic AI output into more natural language. The Prompt Cost Trimmer further reduces the size of prompts, potentially lowering API costs by 30-50%.

You can explore and utilize these tools at https://antigravitytools.app.