Developer Tools — Free Online Utilities
Free online tools for developers and AI users. LLM token counter, API cost calculator, JSON formatter, and more. No registration required.
AI Stack Builder — Find Your Perfect LLM + Vector DB + …
Answer 5 questions about your project, get a tailored AI stack recommendation. LLM choice (GPT-4o / Claude / Gemini / …
Open Tool →Cron Generator & Tester — Bidirectional Cron Expression …
Free online cron expression generator and tester. Convert cron to human-readable description, see the next 5 upcoming …
Open Tool →Dev Combo — URL / Base64 / JWT / Hash Encoder & Decoder
Four essential dev tools in one page: URL encode/decode, Base64 encode/decode, JWT inspector (decode header + payload, …
Open Tool →JSON Formatter / Validator / Minifier
Free online JSON tool. Format, validate, and minify JSON instantly. Supports nested objects, syntax highlighting, error …
Open Tool →JWT Decoder & Validator — Decode Header/Payload + Verify …
Free online JWT decoder and signature validator. Decode header and payload, highlight registered claims …
Open Tool →LLM API Cost Calculator — GPT-4, Claude, Gemini
Calculate LLM API monthly cost. Enter your input/output tokens, requests per day, and pick a model — get instant cost …
Open Tool →LLM Model Recommender 2026 — Pick the Right LLM by Use Case, …
Free decision engine for choosing the right LLM in 2026. Answers 5 questions (use case / budget / context / privacy / …
Open Tool →LLM Token Counter — GPT-4, Claude, Gemini Tokenization …
Free online LLM token counter. Compare how OpenAI GPT-4 / GPT-4o, Anthropic Claude, and Google Gemini tokenize your …
Open Tool →Markdown ↔ HTML Converter
Convert Markdown to HTML or HTML to Markdown instantly. Supports tables, code blocks, links, images. Live preview, …
Open Tool →MCP Tool Builder — Generate Model Context Protocol Tool …
Free online MCP Tool Definition Generator. Paste a Python or TypeScript function signature and get spec-compliant MCP …
Open Tool →OG Card Preview — Facebook / Twitter / LinkedIn Social Share …
Live preview how your link looks when shared on Facebook, Twitter, LinkedIn, and Slack. Paste a URL or fill in OG meta …
Open Tool →Prompt Optimizer — Restructure, Trim Fillers, Save Tokens …
Free online Prompt Optimizer for AI coding agents and LLM workflows. Detects filler words, restructures into the …
Open Tool →Regex Tester — Live Match Highlighting + Capture Groups
Test JavaScript / PCRE regular expressions with live match highlighting, capture groups, and replace preview. Supports …
Open Tool →Schema.org JSON-LD Generator — Article / Organization / FAQ …
Generate copy-paste-ready Schema.org JSON-LD structured data for Article, Organization, FAQPage, Product, and …
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