Free Developer Tools
Free tools for everyday developer tasks. They run entirely in your browser: nothing you paste is sent to a server.
JSON Validator
Free online JSON validator and formatter. Shows the exact line and column of each error and how to fix it, keeps large numbers exact, and runs entirely in your browser.
Open tool →JSON to Java Converter
Convert JSON to Java records, Lombok classes or POJOs online. Correct types for long IDs, dates and decimals, Jackson annotations for snake_case, and code that compiles.
Open tool →CLAUDE.md Generator
Free generator for AGENTS.md, CLAUDE.md, GEMINI.md, Copilot instructions and Cursor rules. Pick your stack and architecture and get a clear instructions file for your AI coding agent.
Open tool →LLM API Cost Calculator
Free calculator for LLM API costs. Compare the price per request, per day and per month of Claude, GPT and Gemini models, with prompt caching, the Batch API and long-prompt pricing.
Open tool →SKILL.md Generator
Free generator for Agent Skills (SKILL.md). Pick your stack and a task such as writing tests, fixing bugs or reviewing changes, and get a ready-to-use skill for Claude Code and other AI coding agents.
Open tool →Need an instructions file for your AI coding agent right away? Browse the CLAUDE.md and AGENTS.md templates for Spring Boot, Next.js, Python and Go.