Free Online Developer Tools

38+ tools that run 100% in your browser. No signup. No data sent to servers.

{ } JSON Formatter Format, validate, and minify JSON. Syntax highlighting with error detection. Developer 🔐 Base64 Encoder/Decoder Encode text to Base64 or decode Base64 strings instantly. Developer .* Regex Tester Test regular expressions with real-time matching, capture groups, and visual highlights. Developer 🔑 JWT Decoder Decode JWT tokens to inspect header, payload, and expiration. No validation. Developer 🔀 UUID Generator Generate v4 UUIDs instantly. Bulk generate up to 100 at a time. Developer ⏰ Cron Parser Parse cron expressions to human-readable schedules and generate cron syntax. Developer # Hash Generator Generate SHA-256, SHA-384, SHA-512, and SHA-1 hashes using Web Crypto API. Developer ✎ Diff Checker Compare two texts side-by-side with line-level diff highlighting. Developer 🕒 Timestamp Converter Convert between Unix epoch timestamps and human-readable dates. Developer 📄 CSV ↔ JSON Convert between CSV and JSON formats with delimiter detection. Developer 🗃 SQL Formatter Format and beautify SQL queries with keyword uppercasing and indentation. Developer ✍ Markdown Preview Write Markdown and see a live rendered preview side-by-side. Developer </> HTML ↔ Markdown Convert HTML to Markdown or Markdown to HTML instantly. Developer 📃 YAML ↔ JSON Convert between YAML and JSON formats with validation. Developer 🔒 .env Redactor Paste .env files and redact secret values for safe sharing. Developer 📈 Meta Tag Generator Generate SEO-optimized meta tags with title, description, and OG tags. SEO 🔬 Schema JSON-LD Generator Generate FAQ, HowTo, Article, Product, and LocalBusiness structured data. SEO 🔍 SERP Preview Preview how your page will look in Google search results. SEO 🤖 Robots.txt Generator Generate and validate robots.txt files for search engine crawlers. SEO 🌐 OG / Twitter Card Preview Preview how your links look when shared on social media. SEO 🔗 UTM Bulk Builder Generate tracked UTM URLs in bulk for marketing campaigns. SEO 📎 Canonical Tag Checker Check if a URL has a canonical tag and whether it points to itself. SEO 🌍 Hreflang Tag Builder Generate hreflang tags for multi-language and multi-region sites. SEO 🔗 Slug Normalizer Clean and normalize URL slugs in bulk. Handles special characters. SEO 📝 Word Counter Count words, characters, sentences, paragraphs, and reading time. Text Aa Case Converter Convert text between UPPER, lower, Title, camelCase, snake_case, and more. Text 🔗 Slug Generator Generate clean URL slugs from any text. Handles accents and special chars. Text 💬 Lorem Ipsum Generator Generate placeholder text by paragraphs, sentences, or words. Text 📋 List Deduper Remove duplicate lines from lists. Sort, trim, and filter blank lines. Text 📈 Markdown Table Builder Build markdown tables visually. Add rows, columns, and alignment. Text ✉ Email Signature Generator Create professional HTML email signatures with social links and images. Generator 🎨 Favicon Generator Generate a full favicon pack (ICO, PNG, Apple Touch) from any image. Generator ▩ QR Code Generator Generate and decode QR codes. Download as PNG or SVG. Generator 🎨 Color Palette Generator Generate harmonious color palettes. Export as CSS, Tailwind, or SCSS. Generator 🔠 Typography Scale Generate a modular type scale. Preview sizes and export as CSS. Generator 🔒 Password Generator Generate strong passwords with a strength meter. Customizable length and chars. Generator ⚪ Color Contrast Checker Check foreground/background color contrast against WCAG AA and AAA standards. Accessibility 🎨 WCAG Palette Generator Generate accessible color palettes that pass WCAG contrast requirements. Accessibility

Why Use DevToolbox?

DevToolbox gives developers, SEO professionals, and content creators fast, free tools that run entirely in the browser. Your data never leaves your machine — there are no servers processing your code, tokens, or text.

Features

Popular Tools

Our most-used tools include the JSON Formatter for validating and beautifying JSON, the Regex Tester for debugging regular expressions, and the JWT Decoder for inspecting tokens. Every tool includes examples and explanations to help you work faster.