Free Online Developer Tools
Fast, private, browser-based. No sign-up required. Works offline.
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JSON Formatter
Prettify, minify, and validate JSON instantly in your browser.
Base64 Encode / Decode
Encode text to Base64 or decode Base64 back to plain text.
UUID Generator
Generate v4 UUIDs instantly — single or batch.
URL Encode / Decode
Encode or decode URL components and query strings.
Text Case Converter
Convert text to UPPER, lower, Title, camelCase, snake_case, and more.
Markdown Preview
Live Markdown editor with real-time HTML preview. Supports GFM tables, task lists, and code blocks.
Color Converter
Convert colors between HEX, RGB, and HSL formats with a live color preview.
Regex Tester
Test regular expressions in real time with match highlighting and capture group details.
Hash Generator
Generate MD5, SHA-1, SHA-256, SHA-384, and SHA-512 hashes from any text.
Timestamp Converter
Convert Unix timestamps to human-readable dates and vice versa. Auto-detects seconds vs milliseconds.
JWT Decoder
Decode and inspect JWT header, payload, and signature. Highlights expiry status and timestamp claims.
Diff Checker
Compare two texts line by line and highlight additions and deletions. Powered by LCS algorithm.
Password Generator
Generate cryptographically secure passwords. Customize length and character sets with entropy meter.
QR Code Generator
Generate QR codes from URLs, text, Wi-Fi credentials, and more. Download as PNG.
Cron Expression Parser
Parse and explain cron expressions in plain English. Preview next 10 scheduled run times.
Lorem Ipsum Generator
Generate Lorem Ipsum placeholder text instantly. Choose paragraph count and copy to clipboard.
Word & Character Counter
Count words, characters, sentences, and paragraphs. Estimate reading and speaking time.
Chmod Calculator
Calculate Linux file permissions interactively. Convert between numeric and symbolic notation.
CSV to JSON Converter
Convert CSV to JSON and JSON to CSV instantly. Handles quoted fields, auto-detects headers.
HTML Entity Encoder / Decoder
Encode and decode HTML entities. Supports named, decimal, and hex entities.
YAML to JSON Converter
Convert YAML to JSON and JSON to YAML instantly. Supports nested objects, arrays, and all YAML 1.2 features.
Line Tools
Remove duplicate lines, sort alphabetically or numerically, reverse, shuffle, and trim text lines.
Number Base Converter
Convert between binary, octal, decimal, and hex number systems.
SQL Formatter
Format, beautify, and minify SQL queries with syntax highlighting.
Aspect Ratio Calculator
Calculate and resize aspect ratios. Lock ratio and scale dimensions proportionally.
XML Formatter
Format, beautify, and minify XML documents with syntax validation.
ASCII Converter
Convert between text and ASCII codes. Supports decimal, hex, and binary representations.
TOML to JSON Converter
Convert between TOML and JSON formats instantly with validation.
Image to Base64 Converter
Convert images to Base64 strings and Data URIs. Supports PNG, JPEG, GIF, and more.
CSS to Tailwind Converter
Convert CSS properties to Tailwind utility classes instantly.
CSS Unit Converter
Convert between px, rem, em, and vw CSS units instantly. Configurable root font size and viewport width.
Markdown Table Generator
Build Markdown tables visually — add rows and columns, paste CSV or JSON, then copy the formatted table.
JSON to TypeScript Generator
Generate TypeScript interfaces from JSON. Handles nested objects, arrays, unions, and optional properties.
Fake Data Generator
Generate realistic test data: names, emails, addresses, UUIDs, and more. Export as JSON or CSV.
URL Parser
Parse any URL into its components: protocol, host, port, path, query parameters, and hash. Instant browser-native parsing.
Slugify String
Convert any text to a URL-friendly slug. Handles Unicode, removes special characters, custom separator support.
HTTP Status Codes
Searchable reference for all HTTP status codes (1xx–5xx) with descriptions and use cases.
HMAC Generator
Generate HMAC signatures using SHA-256, SHA-384, or SHA-512. Hex and Base64 output. Runs entirely in your browser.
cURL to Code Converter
Convert cURL commands to Python, JavaScript, Go, PHP, and Node.js code instantly.
JSON to Zod Schema
Generate Zod validation schemas from JSON data. Handles nested objects, arrays, and optional properties.
Docker Run to Compose
Convert docker run commands to docker-compose.yml. Supports ports, volumes, env vars, networks, and more.
RSA Key Pair Generator
Generate RSA key pairs (2048/4096-bit) in PEM or JWK format. 100% client-side — keys never leave your browser.
TOTP Generator
Generate RFC 6238 TOTP codes with live countdown. Configurable algorithm, digits, and period. Includes QR code.
JSON Diff
Compare two JSON objects and visualize differences. Outputs RFC 6902 JSON Patch and a color-coded tree diff.
Env File Parser
Parse .env files online — visualize key-value pairs, detect errors, and export to JSON. 100% client-side.
YAML Validator
Validate YAML syntax online — detailed error messages with line and column numbers, plus parsed structure preview. 100% client-side.
JSON Schema Validator
Validate JSON data against a JSON Schema online. Supports Draft-07 and Draft 2020-12. Shows error paths and detailed messages. 100% client-side.
.htaccess Generator
Generate Apache .htaccess configurations online. Force HTTPS, set caching, block directory listing, add custom redirects. 100% client-side.
Robots.txt Generator
Generate robots.txt files online. Configure user-agent rules, allow/disallow paths, and sitemap URLs. 100% client-side.
SVG to PNG Converter
Convert SVG files to PNG online. Upload or paste SVG code, choose output size and background. 100% client-side Canvas API.
WebP Converter
Convert PNG/JPG/GIF to WebP and WebP to PNG online. Batch conversion, quality control, file size comparison. 100% client-side.
CSS Variables Generator
Generate CSS custom properties from design tokens. Define colors, typography, spacing, and border radius — output ready-to-use :root variables.
Why ZeroTool?
Privacy First
All computation runs in your browser. Zero server requests. Your data never leaves your device.
Lightning Fast
Zero JavaScript framework overhead. Static pages served from Cloudflare's global CDN edge network.
Natively Multilingual
Built from the ground up in English, Chinese, Japanese, and Korean. Not translated — natively crafted for each audience.
Latest Articles
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JSON Diff Online: Compare JSON Structures and Detect Config Drift
Compare two JSON objects online and see exactly what changed — added, removed, and modified keys. Learn tree diff vs text diff, RFC 6902 JSON Patch, and real-world use cases.
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RSA Key Pair Generator Online: Generate 2048 & 4096-bit Keys in Your Browser
Generate RSA key pairs (PEM, JWK) instantly in your browser — no server, no upload. Learn key sizes, formats, and real-world use cases for SSH, TLS, and JWT.
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TOTP Generator & 2FA Explained: How Time-Based One-Time Passwords Work
Learn how TOTP and 2FA work under RFC 6238. Generate test TOTP codes online, understand HMAC + time steps, and implement 2FA in your app.