Free Online Developer Tools
100+ utilities for encoding, converting, formatting, generating, and transforming data. Everything runs in your browser with no data sent to any server.
Encode & Decode
12 tools
Base64 Encode / Decode
Convert text to Base64 or decode Base64 strings back to readable text. Works offline.
URL Encode / Decode
Convert special characters to percent-encoded format for URLs. Decode encoded URLs back to readable text.
HTML Entity Encode / Decode
Escape HTML special characters or decode entities. Prevent XSS and display reserved characters safely.
JWT Parser & Decoder
Parse JSON Web Tokens. View header, payload claims, and check expiration status.
String Escape / Unescape
Escape strings for JSON and JavaScript. Convert special characters to safe escape sequences like \n, \t, \u00A9.
Hash Generator
Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from any text input.
Image to Base64 Converter
Convert images to Base64-encoded data URIs for embedding in HTML and CSS.
Base64 to Image Converter
Decode Base64 strings back to viewable and downloadable images.
Text to Binary Converter
Convert text to binary, hex, octal, decimal and vice versa.
Salted Hash Generator
Generate salted SHA-256 and SHA-512 hashes with configurable iteration count using the Web Crypto API.
HMAC Generator
Generate HMAC authentication codes using SHA-256, SHA-384, and SHA-512.
AES Encryption / Decryption
Encrypt and decrypt text using AES-GCM with the Web Crypto API.
Converters
21 tools
CSV to JSON Converter
Convert CSV data into structured JSON arrays or objects with automatic header detection.
JSON to CSV Converter
Convert JSON arrays into CSV format for use in spreadsheets and databases.
YAML to JSON Converter
Convert YAML configuration files to JSON format for APIs and tools.
JSON to YAML Converter
Convert JSON data to YAML format for configuration files and readability.
XML to JSON Converter
Transform XML documents into JSON format for modern API integration.
Timestamp to Date Converter
Convert Unix timestamps to human-readable dates and vice versa.
HEX to RGB Converter
Convert between HEX, RGB, and HSL color formats with live preview.
RGB to HEX Converter
Convert RGB color values to HEX color codes with live preview and CSS output.
RGBA to HEX Converter
Convert RGBA color values with transparency to 8-digit HEX color codes.
Number Base Converter
Convert numbers between binary, octal, decimal, and hexadecimal systems.
CSS Units Converter
Convert between CSS units - px to rem, em, pt, and percent.
Byte / Unit Converter
Convert between bytes, KB, MB, GB, TB, PB and their binary equivalents (KiB, MiB, GiB, TiB, PiB).
HTML to Markdown Converter
Convert HTML markup to clean Markdown syntax for documentation and content.
JSON to TypeScript Interface
Generate TypeScript interfaces and types from JSON data automatically.
Query Parameters to JSON
Parse URL query strings into structured JSON objects instantly.
TOML ↔ JSON Converter
Convert between TOML and JSON configuration formats instantly.
SVG to JSX Converter
Convert SVG markup to JSX-compatible React components.
JSON to Go Struct
Generate Go struct definitions from JSON data automatically.
Temperature Converter
Convert between Celsius, Fahrenheit, and Kelvin temperature scales.
Docker Run to Compose
Convert docker run commands to docker-compose.yml format.
Roman Numeral Converter
Convert between Roman numerals and Arabic (decimal) numbers.
Formatters & Minifiers
9 tools
JSON Formatter & Validator
Format, validate, and minify JSON data with error detection and proper indentation.
SQL Minifier & Formatter
Minify SQL queries by removing comments and whitespace, or format them for readability.
JavaScript Formatter & Minifier
Beautify or minify JavaScript code with customizable formatting options.
JSON Diff & Compare
Compare two JSON objects and highlight structural and value differences.
XML Formatter & Validator
Format, prettify, minify, and validate XML documents.
JSONPath Tester
Test JSONPath expressions against JSON data and view matched results.
HTML Formatter & Beautifier
Beautify, format, or minify HTML code with proper indentation
CSS Formatter & Beautifier
Beautify, format, or minify CSS code with proper indentation
Code Syntax Highlighter
Syntax-highlight code for blogs, presentations, and documentation. Copy as styled HTML.
Generators
14 tools
UUID Generator
Generate random UUID v4 identifiers for databases, sessions, and tracking.
Random String Generator
Generate cryptographically secure random strings for API keys, tokens, and passwords.
Lorem Ipsum Generator
Generate placeholder text for design mockups and layout testing.
Password Generator
Generate strong, secure passwords with customizable length and character rules.
QR Code Generator
Generate QR codes from text, URLs, Wi-Fi credentials, and contact info.
URL Slug Generator
Generate clean, SEO-friendly URL slugs from any text with transliteration support.
Meta Tag Generator
Generate HTML meta tags and Open Graph tags for SEO and social media sharing.
Cron Expression Parser
Parse cron expressions into human-readable schedules with next run times.
TOTP Code Generator
Generate and verify time-based one-time passwords (TOTP) for two-factor authentication.
WiFi QR Code Generator
Generate WiFi connection strings and printable cards for easy network sharing.
Password Strength Analyzer
Analyze password strength with entropy and crack-time estimates
Coin Flip & Dice Roller
Flip coins and roll dice with true randomness. Visual animations, statistics, and multi-dice support.
List Randomizer & Shuffler
Randomize, shuffle, sort, and pick random items from any list. Fisher-Yates algorithm with true randomness.
Corrupt File Generator
Generate dummy corrupted files for testing. Correct file headers with random data for upload validation testing.
Text Tools
9 tools
Regex Tester
Test regular expressions with real-time matching, capture groups, and flag support.
Text Diff Checker
Compare two texts side by side and highlight the differences line by line.
Text Case Converter
Convert text between camelCase, snake_case, PascalCase, UPPERCASE, and more.
Word & Character Counter
Count words, characters, sentences, paragraphs, and estimate reading time.
Markdown Preview
Write and preview Markdown with live rendering.
Emoji Picker & Search
Search, browse, and copy emojis by category with Unicode info
Text to NATO Phonetic Alphabet
Convert text to NATO phonetic alphabet with Morse code
Remove Line Breaks
Remove or add line breaks in text. Strip empty lines, trim whitespace, and normalize text formatting.
Number & List Sorter
Sort numbers and text lists with multiple algorithms. Natural sort, numeric, alphabetical, and by length.
CSS & Design
10 tools
CSS Gradient Generator
Create beautiful CSS linear and radial gradients with a visual editor.
CSS Box Shadow Generator
Design box shadows visually with controls for offset, blur, spread, and color.
Border Radius Preview
Visually edit CSS border-radius for each corner with live preview.
Color Palette Generator
Generate harmonious color palettes using color theory algorithms.
Color Blindness Simulator
Simulate how colors appear to people with different types of color vision deficiency.
WCAG Color Contrast Checker
Check if color combinations meet WCAG 2.1 accessibility contrast requirements.
Flexbox Playground
Interactive CSS Flexbox sandbox to experiment with all flex container and item properties.
CSS Inliner for Email
Convert CSS stylesheets to inline styles for HTML email compatibility.
Tailwind CSS to Vanilla CSS
Convert Tailwind CSS utility classes to standard vanilla CSS properties.
Universal Color Picker & Converter
All-in-one color picker converting between HEX, RGB, HSL, HSV, CMYK
Image Tools
12 tools
Image Resizer
Resize images to specific dimensions while preserving quality and aspect ratio.
WebP Image Converter
Convert images to WebP format for smaller file sizes and faster web loading.
SVG Viewer & Editor
Preview, validate, and optimize SVG code with live rendering.
Image Blur Tool
Apply Gaussian blur to images with adjustable intensity. Preview results in real time and download instantly.
Image Crop Tool
Crop images with pixel-perfect precision. Set custom crop areas, use aspect ratio presets, and download cropped results.
Image Color Inverter
Invert colors of any image. Create negative effects with per-channel control and instant preview.
Image Grayscale Converter
Convert images to black and white. Multiple grayscale algorithms with adjustable intensity.
Image Pixelate Tool
Pixelate images with adjustable pixel block size. Create mosaic effects and censor content easily.
Image Brightness & Contrast
Adjust image brightness, contrast, and saturation. Real-time preview with preset adjustments.
Image Rotate & Flip
Rotate and flip images with ease. 90°/180° rotations, custom angles, and horizontal/vertical flipping.
Color Picker from Image
Pick colors from any image. Click to extract HEX, RGB, and HSL values with a magnified preview.
Image Merge & Combine
Combine multiple images into one. Horizontal, vertical, or grid layouts with customizable gaps.
Data & Utilities
13 tools
CSV File Viewer
View, sort, and filter CSV files in a spreadsheet-like table interface.
Chmod Calculator
Calculate Unix file permissions - convert between symbolic and numeric chmod notation.
Aspect Ratio Calculator
Calculate and convert aspect ratios for images, videos, and responsive design.
IPv4 Subnet Calculator
Calculate network address, broadcast, host range, and CIDR for IPv4
HTTP Status Codes Reference
Interactive searchable guide to all HTTP status codes
Percentage Calculator
Multiple percentage calculation modes with visual results
URL Parser & Analyzer
Parse URLs into components: protocol, host, path, query, hash
User-Agent Parser
Parse user-agent strings to identify browser, OS, and device
Keyboard Event Keycode Info
Press any key to see keyCode, key, code, and modifier states
MIME Types Lookup
Search MIME types by file extension or content type
Math Expression Evaluator
Evaluate math expressions with functions like sqrt, sin, cos, log
ETA Calculator
Calculate estimated time remaining and completion for tasks
Device Information
View current device, browser, screen, and connection details
Why Developers Choose DevTools Online
When you're debugging API responses at 2am, you need tools that work immediately without registration forms or payment walls. That's why we built this collection. Whether you're formatting a massive JSON payload from a production error log, converting Base64-encoded images from an API response, or testing regex patterns for input validation, these tools handle the job without interruption.
Every tool runs in your browser. Your data stays on your machine. Need to decode a JWT token containing sensitive user data? Parse a CSV file with customer information? Generate a UUID for a database migration? Hash a password for testing? Do it here. Nothing gets uploaded, logged, or stored on any server. This matters when you're working with production data, API keys, or anything that shouldn't leave your local environment.
The toolkit covers daily development tasks across multiple domains. Format and validate JSON, XML, SQL, and YAML. Convert between CSV, JSON, and XML formats. Encode and decode Base64, URL parameters, HTML entities, and JWT tokens. Generate UUIDs, random passwords, Lorem Ipsum text, and QR codes. Test regular expressions with real-time matching. Compare text with diff highlighting. Calculate MD5, SHA-1, SHA-256, and SHA-512 hashes. Convert colors between HEX, RGB, HSL, and CMYK. Create CSS gradients and box shadows. Resize, crop, and optimize images. The list goes on.
Built with Next.js and TypeScript, optimized for performance. No ads, no tracking pixels, no analytics cookies, no newsletter popups. Just open a tool and use it. Bookmark the ones you need frequently. Works on desktop, tablet, and mobile. All 100+ tools are free and always will be.