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FREE ONLINE TOOLS

💻 Free Developer Tools

Browse 94 free developer tools on FastTool. All tools run in your browser with no signup required.

About Our Developer Tools

Whether you are debugging JSON, testing regular expressions, encoding data, or generating boilerplate code, developer tools can save hours of manual work. FastTool's free developer tools run entirely in your browser so your source code and API keys never leave your machine. From formatters and validators to encoders and generators, every tool is designed for the workflows that software engineers, front-end developers, and back-end programmers face daily. No IDE plugins to install, no CLI dependencies to manage, and no signup walls. Open a tool, paste your input, and get instant results. Each utility supports keyboard shortcuts, one-click copy, and works on any device with a modern browser.

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All Developer Tools (94)

JSON Formatter & Validator Popular

Format JSON, minify, and find errors with line-level feedback.

Base64 Encode/Decode

Encode text to Base64 or decode Base64 back to text.

Regex Tester

Test regex patterns and view matches with their indices.

UUID Generator

Generate UUID v4 with one click, supports bulk generation.

JWT Decoder

Decode JWT tokens and view header, payload, and expiry details.

SQL Formatter

Format and beautify SQL queries with proper indentation.

HTML to Markdown

Convert HTML markup to clean Markdown text.

Timestamp Converter

Convert between epoch timestamps and human-readable dates.

Unix Time Converter

Convert between Unix timestamps and dates in both directions.

URL Encode/Decode

Safely encode and decode URL parameters for query strings.

HTML Entity Encoder/Decoder

Convert HTML special characters to entities or decode them back.

JSON Validator

Validate JSON with detailed error messages, line numbers, and fix suggestions.

Live HTML Editor

Write HTML, CSS, and JS with real-time preview side by side.

CSS Flexbox Generator

Visually generate CSS flexbox layouts with live preview. Copy the generated CSS instantly.

CSS Grid Generator

Build CSS Grid layouts visually — set columns, rows, gap, and column width template, then copy the ready CSS.

Text Diff / Compare

Compare two texts and view differences line by line.

Diff Checker

Compare two text blocks with enhanced diff highlighting.

Number Base Converter

Convert between binary, octal, decimal, and hexadecimal.

ASCII Art Generator

Convert text to ASCII art with multiple font styles.

Morse Code Translator

Convert text to Morse code or decode Morse code to text.

Pixel to REM Converter

Convert pixels to REM and REM to pixels with custom base font size.

Text to Binary Converter

Convert text to binary code and binary back to text instantly.

JSONPath Tester

Test JSONPath expressions against JSON data.

YAML to JSON

Convert YAML to JSON and JSON to YAML instantly.

CSS Minifier

Minify CSS code to reduce file size.

JavaScript Minifier

Minify JavaScript code for production.

XML Formatter

Format and validate XML documents with syntax highlighting.

Invisible Character Detector

Find and remove zero-width and invisible Unicode characters.

Image to Base64

Convert images to Base64 encoded strings.

Screenshot to Code

Extract colors and layout hints from screenshots.

JSON to YAML Converter

Convert JSON to YAML and YAML to JSON instantly.

JWT Generator

Generate JWT tokens with custom header and payload.

API Tester

Simple REST API tester supporting GET, POST, PUT, DELETE requests.

Regex Generator

Generate regex patterns from plain English descriptions.

HTTP Status Codes

Reference guide for HTTP status codes with search and filtering.

HTML Table Generator

Generate HTML tables with custom rows and columns.

JSON Schema Generator

Generate JSON Schema from sample JSON data.

XML to JSON

Convert XML data to JSON format instantly.

TOML to JSON

Convert TOML configuration files to JSON format.

Epoch Converter

Convert between epoch timestamps and human-readable dates with millisecond precision.

URL Parser

Parse URLs into components like protocol, host, path, and query parameters.

User Agent Parser

Parse user agent strings into browser, OS, and device details.

cURL to Code

Convert a cURL command into JavaScript fetch, Python requests, or PHP code instantly.

Regex Cheat Sheet

Interactive regex quick-reference with live test area — learn and test common patterns instantly.

JSON to TypeScript

Generate TypeScript interfaces from JSON — paste your JSON and get a clean, typed interface instantly.

CSS Animation Generator

Build CSS @keyframes animations visually — pick a preset, set duration and easing, then copy ready code.

HTML Minifier

Minify HTML by removing comments and collapsing whitespace — see byte savings instantly in the browser.

Git Commit Message Generator

Generate clean, conventional Git commit messages — pick a type, scope, and description to get a ready-to-use commit message.

HTML to JSX Converter

Convert HTML code to JSX/React syntax — transforms class to className, style strings to objects, and self-closes tags.

JWT Debugger

Decode and inspect JWT tokens — view header, payload, expiration status, and claims without a secret key.

Unix Timestamp Converter

Convert Unix timestamps to human-readable dates and dates back to Unix timestamps with timezone support.

CSS Clip-Path Generator

Generate CSS clip-path shapes — choose polygon, circle, ellipse, or inset presets and copy the CSS code instantly.

Fake Data Generator

Generate realistic fake data for testing — names, emails, phone numbers, addresses, UUIDs, dates, and more in bulk.

CSS Specificity Calculator

Calculate the specificity of any CSS selector — understand which rules win and why, with a clear a-b-c breakdown.

Barcode Generator

Generate Code 39 barcodes instantly in your browser — enter text or numbers and download as PNG. No sign-up required.

.gitignore Generator

Generate a ready-to-use .gitignore file for any language or framework — Node.js, Python, Java, Go, Rust, Swift, and more.

JSON to SQL

Convert JSON objects or arrays into SQL INSERT statements — supports MySQL, PostgreSQL, SQLite, and generic SQL dialects.

CSS Unit Converter

Convert CSS units instantly — px, em, rem, vw, vh, pt, pc, cm, mm, and inches with custom base font size and viewport dimensions.

Binary to Text Converter

Convert binary code to readable text (ASCII) and text back to binary — supports space-separated 8-bit binary, hex input, and bulk conversion with copy output.

HTML Entities Reference

Searchable reference for all HTML entities — find the HTML code, decimal, hex, and Unicode for any symbol, arrow, math operator, currency sign, or special character.

CSS Triangle Generator

Generate CSS-only triangles using border tricks — choose from 8 directions, pick color and size, then copy the ready-to-use CSS snippet with live preview.

HTML to Plain Text

Strip HTML tags from any code and extract clean plain text — removes all markup, decodes HTML entities, and preserves or collapses whitespace for readable output.

File Size Converter

Convert file sizes between bytes, kilobytes, megabytes, gigabytes, terabytes, and petabytes using either binary (1024) or decimal (1000) base — see all units at once.

Bandwidth & Transfer Time Calculator

Calculate how long it takes to download or upload a file based on connection speed — or find the maximum file size transferable in a given time.

Git Cheat Sheet

Searchable Git commands reference — find any git command by name or description instantly, with syntax and explanations across setup, branching, remote, stash, undo, and more.

CSS Variables Generator

Build a complete CSS custom properties design token system — define colors, spacing, typography, and border radius values and get a ready-to-paste :root {} block.

CSS Filter Generator

Generate CSS filter properties with a live visual preview — adjust blur, brightness, contrast, saturation, hue-rotate, sepia, grayscale, and invert with interactive sliders.

HTML Beautifier

Beautify and format messy or minified HTML — paste compressed HTML and get properly indented, readable code with configurable indentation style in one click.

ASCII Table Generator

Convert CSV or tab-separated data into beautifully formatted ASCII text tables — paste your data, choose a border style, and copy the plain-text table for documentation or terminal output.

JSON Minifier

Minify JSON by removing all whitespace, line breaks, and comments — paste any formatted or pretty-printed JSON and get the smallest possible valid JSON string in one click.

Phone Number Validator

Validate and format phone numbers — check if a phone number is valid, detect country code, format to E.164 and international notation, and see the number type.

CSS Reset Generator

Generate a customized CSS reset or normalize stylesheet — choose from popular presets (Eric Meyer, Normalize.css, Modern CSS Reset, Tailwind Preflight) or build your own.

Variable Name Generator

Convert any phrase into all standard variable naming conventions — camelCase, PascalCase, snake_case, SCREAMING_SNAKE, kebab-case, and more — in one click.

Color to Tailwind CSS

Find the nearest Tailwind CSS color class for any hex, RGB, or HSL color — paste your color and instantly get the closest Tailwind palette match with the class name to use.

JSON to XML Converter

Convert JSON data to well-formatted XML instantly — paste any valid JSON and get clean XML output with proper indentation, attributes, and root element wrapping.

QR Code Scanner

Scan and decode QR codes directly in your browser — upload an image containing a QR code and instantly extract the encoded text, URL, or data without any app needed.

Keyboard Tester

Test every key on your keyboard directly in the browser — press any key to see its key code, key name, and event properties. Perfect for debugging keypress events and checking keyboard functionality.

Mermaid Diagram Editor

Create flowcharts, sequence diagrams, Gantt charts, and more with Mermaid syntax. Live preview updates as you type. Export as SVG.

CSS Transform Generator

Visually generate CSS transform properties. Adjust translate, rotate, scale, and skew sliders to see a live preview and copy the CSS output.

Changelog Generator

Generate a formatted changelog from your commit messages or release notes. Supports Keep a Changelog format, markdown output, and semantic versioning grouping.

CSS Media Query Generator

Generate CSS media queries for responsive design. Choose common device breakpoints or enter custom min/max widths and orientations. Copy the ready-to-use CSS snippet.

SQL Query Builder

Build SQL SELECT queries visually without writing raw SQL. Enter table name, choose columns, add WHERE conditions, ORDER BY, and LIMIT — get the query instantly.

API Response Formatter

Format, validate, and analyze API responses. Paste raw JSON or XML to get a pretty-printed, syntax-highlighted version. See response size, key count, and nested structure depth.

README Generator

Generate a professional README.md file for your GitHub project. Enter your project name, description, tech stack, installation steps, and usage instructions to get a formatted markdown README instantly.

ASCII to Hex Converter

Convert ASCII text to hexadecimal and back. Supports spaces, punctuation, and special characters. See decimal, octal, and binary representations alongside hex. Perfect for developers and encoding tasks.

License Generator

Generate open source license text for your project. Choose from MIT, Apache 2.0, GPL v3, BSD, ISC, Unlicense, or CC0. Enter your name and year to get the complete license ready to add to your project.

JSON to Table

Convert JSON arrays into a formatted HTML table instantly. Paste any JSON array and see it as a clean, readable table with column headers auto-detected from keys. Export as HTML or copy as TSV.

CSS Selector Tester

Test CSS selectors against an HTML snippet in real time. Enter your HTML, type a CSS selector, and instantly see which elements match — with match count, tag names, classes, and IDs listed.

JSON to Go Struct

Convert any JSON object into Go struct types instantly. Paste your JSON and get clean, idiomatic Go struct definitions with proper field names, types, and json tags. Supports nested objects and arrays.

HTML Form Builder

Build HTML forms visually without writing code. Add fields like text, email, password, select, checkbox, radio, and textarea. Configure labels, placeholders, and required flags. Preview instantly and copy the generated HTML.

GitHub README Generator

Generate a professional GitHub profile README.md in seconds. Fill in your name, title, bio, skills, and social links — get a beautifully formatted Markdown file with badges, stats sections, and a personalized introduction ready to copy.

Dockerfile Generator

Generate production-ready Dockerfiles for your projects. Choose your language or framework (Node.js, Python, Go, Java, PHP, Ruby, and more), configure ports, environment variables, and build options to get a clean, optimized Dockerfile.

Text to Table Converter

Convert comma-separated, tab-separated, or pipe-delimited text into formatted HTML or Markdown tables instantly. Paste your raw data, choose a delimiter, and get a clean table ready to use in web pages, documentation, or GitHub.

JavaScript Obfuscator

Obfuscate your JavaScript code to make it harder to reverse-engineer. Renames variables and functions to short meaningless names, encodes string literals, removes comments, and minifies whitespace — all client-side with no code ever sent to a server.

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