Free Online Developer Tools

Count tokens and estimate cost across GPT, Claude, Gemini, and Llama

Parse and replay raw LLM SSE logs from OpenAI, Anthropic, Ollama, and Vercel AI SDK

Render LLM prompts with variables across Simple, Handlebars, Jinja, and LangChain syntaxes

Compare 2–4 LLM outputs side by side with diff, metrics, and Markdown / JSON rendering

Design LLM tool schemas visually and export to OpenAI, Anthropic, Zod, and TypeScript

Connect to MCP servers and test tools via JSON-RPC

Beautify, minify, and validate JSON data with syntax highlighting

Encode and decode Base64 strings instantly

Generate UUID v1, v4, and v7 with custom formats

Encode and decode URLs with percent-encoding

Decode JWT tokens and inspect Header, Payload, and Signature

Generate MD5, SHA-1, SHA-256, SHA-512 hashes

Test regular expressions with real-time match highlighting

Convert colors between HEX, RGB, and HSL formats

Convert between Unix timestamps and human-readable dates

Live preview Markdown with GFM support

Format and beautify SQL queries with dialect support

Format, beautify, and minify HTML code

Format, beautify, and minify CSS code

Minify JavaScript and JSON code

Convert between JSON and YAML formats

Convert between JSON arrays and CSV format

Convert between JSON and XML formats

Convert between binary, octal, decimal, and hexadecimal

Convert images between PNG, JPEG, and WebP formats

Convert between units of length, weight, temperature, and more

Encode and decode HTML entities like & < >

Convert text to \uXXXX Unicode escapes and back

Generate secure random passwords with customizable options

Generate placeholder text in paragraphs, sentences, or words

Generate QR codes from text or URLs with download options

Generate and parse cron expressions with next execution times

Compare two texts and highlight differences line by line

Test JSONPath expressions with real-time matching

Edit HTML, CSS, and JS with real-time iframe preview