Free Online Developer Tools

DevToolBelt is a collection of free online developer tools designed to make your daily coding workflow faster and more efficient. Whether you are debugging an API response, working with authentication tokens, or generating unique identifiers, our tools handle it instantly — right in your browser.

Every tool on DevToolBelt runs entirely on the client side. That means your data never touches our servers. There is no upload, no storage, no tracking of your input. Your JSON payloads, Base64 strings, JWT tokens, and timestamps stay on your machine and are processed by your browser alone. This makes DevToolBelt one of the most privacy-respecting developer tool platforms available.

Our JSON formatter and validator helps you beautify minified JSON from API responses, config files, or databases. The Base64 encoder and decoder handles UTF-8 text correctly, making it perfect for working with API authentication headers and data URIs. Need unique IDs? The UUID generator creates cryptographically random v4 UUIDs individually or in bulk, with options for formatting.

The Unix timestamp converter is essential for anyone working with logs, databases, or APIs that use epoch time. It auto-detects whether you are working with seconds or milliseconds and displays results in multiple formats. And the JWT decoder lets you inspect token headers, payloads, and claims — including expiration status — without needing any external libraries.

For developers working with AI and LLMs, we offer specialized tools including an AI token counter that estimates token usage across GPT-4, Claude, and Gemini models. The JSON Schema generator creates valid schemas from sample data — perfect for OpenAI function calling and Anthropic tool use definitions. And the AI API cost calculator lets you compare pricing across all major providers to find the most cost-effective model for your project.

DevToolBelt is built with modern web technologies including Next.js, TypeScript, and Tailwind CSS. It is fast, responsive, and works seamlessly on desktop and mobile devices. We are constantly adding new tools based on what developers need most. Bookmark this page and come back whenever you need a quick, reliable developer utility.