Free Online Developer Tools
156 browser-based utilities. Fast, private, no signup required.
This page is for developers, students, and anyone who needs a quick utility without installing software. Everything runs locally in your browser: we do not upload your pasted JSON, text, or secrets to our servers.
Scroll the categories below to jump straight to a tool, or use the discovery links at the bottom to browse hubs (JSON tools, HTTP tools, encoding, text, color, and more) and full indexes when you want every page in one list.
JSON & Data
JSON Formatter
Format, validate & minify JSON
JSON Path Finder
Explore JSON structure & find paths
JSON to CSV
Convert JSON arrays to CSV format
CSV to JSON
Convert CSV data to JSON format
JSON to TypeScript
Generate TS interfaces from JSON
JSON Schema Generator
Generate JSON Schema from JSON data
JSON to YAML
Convert JSON to YAML format
YAML to JSON
Convert YAML to JSON format
Fake Data Generator
Generate mock data for testing
JSON Escape / Unescape
Escape & unescape strings for JSON
JSON Flatten
Flatten nested JSON to dot notation
JSON Key Extractor
Extract all unique keys from JSON
JSON Sort Keys
Sort JSON object keys alphabetically
JSON Remove Duplicates
Deduplicate JSON arrays & objects
URL Query Parser
Parse & build URL query strings
Text & String
Word Counter
Count words, characters & sentences
Case Converter
Transform text between cases
Lorem Ipsum
Generate placeholder text
Slug Generator
Convert text to URL-friendly slugs
Whitespace Remover
Clean & strip whitespace from text
Diff Checker
Compare two texts & highlight differences
Text to Binary
Convert text to binary, hex & octal
Morse Code
Translate text to Morse code & back
Unicode Converter
Code points, UTF-8 bytes, character names
ASCII Converter
Text ↔ ASCII codes, decimal, hex, octal, binary
HTML Entity Decoder
Encode & decode HTML entities
Unicode Escape Decoder
Decode \uXXXX, \u{1F600}, %uXXXX
Encoding & Crypto
Base64 Codec
Encode & decode Base64 strings
Base64 Encode
Encode text to Base64 with UTF-8 support
Base64 Decode
Decode Base64 to plain text instantly
URL Encoder
Encode & decode URL components
Hash Generator
Generate MD5, SHA-1 & SHA-256 hashes
Hash Identifier
Identify hash algorithm from string
Password Generator
Generate strong random passwords
Password Breach Checker
Check if password was leaked (HIBP)
Password Entropy Visualizer
Entropy bits, crack time, pattern detection
JWT Decoder
Decode & inspect JSON Web Tokens
JWT Signature Verifier
Verify JWT signatures (HMAC/RSA)
TLS Certificate Decoder
Decode PEM certificates
Public Key Fingerprint
SHA-256 & MD5 key fingerprints
ROT13
Encode & decode ROT13, ROT5, ROT47
UUID Generator
Generate v4 UUIDs instantly
Passphrase Generator
Generate random word passphrases
CSS & Design
CSS Gradient Generator
Build beautiful CSS gradients visually
Box Shadow Generator
Design CSS box shadows with layers
Border Radius Generator
Create CSS rounded corners visually
Color Palette Generator
Create color schemes from any color
Hex to RGB
Convert HEX colors to RGB, HSL & more
Color Converter
Convert between HEX, RGB & HSL
Color Contrast Checker
Check WCAG color contrast compliance
Placeholder Images
Generate placeholder image URLs
Conversion
Markdown Preview
Live preview of Markdown text
Markdown Table Formatter
Format, align & sort markdown tables
Markdown to HTML
Convert Markdown to raw HTML code
HTML to Markdown
Convert HTML to Markdown syntax
JSON to XML
Convert JSON objects into valid XML
XML to JSON
Convert XML documents into JSON
Image to Base64
Encode images to Base64 strings
Px to Rem
Convert pixels to rem & em units
File Size Converter
Convert between KB, MB, GB, TB & more
Temperature Converter
Convert °C, °F & Kelvin instantly
Developer
Regex Tester
Test regex patterns with live matching
Cron Parser
Parse cron expressions to human-readable
SQL Formatter
Format & beautify SQL queries
GraphQL Formatter
Format & minify GraphQL queries
Number Base Converter
Convert between binary, octal, decimal & hex
Subnet Calculator
Calculate subnet masks, ranges & hosts
Unix Permissions
Calculate chmod & file permissions
QR Code Generator
Generate QR codes from any text or URL
HTTP Header Viewer
Inspect request & response headers
HTTP Status Lookup
Look up HTTP status codes & fixes
Gitignore Generator
Generate .gitignore for any project
API Request Builder
Build & test HTTP requests visually
cURL Generator
Generate & parse cURL commands
CORS Checker
Check CORS headers for any URL
Cookie Parser
Parse & build HTTP Set-Cookie headers
HTTP Header Diff
Compare two sets of HTTP headers
Redirect Checker
Follow & inspect URL redirect chains
Calculators
Date Calculator
Days between dates & date math
Percentage Calculator
Calculate percentages & tips
Aspect Ratio Calculator
Calculate & convert aspect ratios
Timestamp Converter
Convert Unix timestamps & dates
Age Calculator
Calculate exact age, zodiac & next birthday
Mortgage Calculator
Monthly payments, interest & amortization
ROI Calculator
Return on investment & annualized ROI
Compound Interest
Growth projections with contributions
Tip Calculator
Calculate tips & split bills easily
Work Hours Calculator
Track hours, breaks & weekly totals
Time Duration Calculator
Duration between times or add durations
Savings Calculator
Project savings growth with contributions
Loan Repayment Calculator
Amortization schedule & extra payments
Investment Growth Calculator
Project investment returns over time
Text & Content
Sentence Counter
Count sentences, avg length & reading level
Paragraph Generator
Generate placeholder paragraphs
Title Case Converter
Title, camel, snake, kebab & more
Hashtag Generator
Generate hashtags from text or topics
Twitter Character Counter
Tweet & bio character limits
Keyword Density Checker
Word frequency & keyword density
Remove Duplicate Lines
Remove or highlight duplicate lines
Sort Text
Sort lines alphabetically or by length
Email Extractor
Extract emails, URLs & phones from text
SEO & Web
PDF Tools
Image Tools
Image Compressor
Compress JPEG, PNG & WebP images
WebP to PNG
Convert WebP to PNG format
PNG to JPG
Convert PNG to JPEG format
SVG Viewer
View, inspect & convert SVG files
Favicon Generator
Generate favicons from any image
Blur Image
Add blur effects to images
Image Color Picker
Pick colors from uploaded images
Remove EXIF Data
Strip metadata & GPS from photos
Random Generators
Random Username Generator
Unique usernames for gaming & social
Random Color Generator
Random colors with HEX, RGB, HSL
Random Number Generator
Numbers, dice rolls & coin flips
Random Name Generator
First & last names by nationality
Random Team Generator
Shuffle & split into random teams
Random Emoji Generator
Pick random emojis by category
Network & Infrastructure
Subnet Calculator
Calculate subnet masks & ranges
CIDR Calculator
Network, broadcast & host range from CIDR
IP Range Calculator
Calculate IP ranges & CIDR blocks
IP Lookup
Geolocation, ISP, timezone for any IP
User Agent Parser
Detect browser, OS & device from UA
DNS Lookup
Query DNS records via Cloudflare DoH
Port Checker
Common port reference & service lookup
SSL Expiration Checker
Check SSL certificate expiry & countdown
Web3 & Crypto
ETH Unit Converter
Convert between Wei, Gwei & Ether
Gas Fee Calculator
Calculate Ethereum gas costs
Token Decimal Calculator
Raw token amounts to readable values
Wallet Checksum Generator
Validate & checksum ETH addresses
Solidity ABI Encoder
Encode function selectors & params
Keccak256 Generator
Multi-hash generator
AI & Prompt Tools
Prompt Tokenizer
Estimate token count for AI prompts
Prompt Optimizer
Analyze prompts & get improvement suggestions
Prompt A/B Tester
Compare two prompt variants side by side
Prompt Temperature Simulator
See how temperature affects output (simulation)
Token Counter
Count tokens & context window usage
OpenAI Cost Calculator
API costs for GPT-4o, o1 & more
Prompt Randomizer
Generate prompt variations from templates
Data Viewers
Date & Time
ISO 8601 Validator
Validate & parse ISO 8601 date strings
RFC 2822 Converter
Convert RFC 2822 email date formats
Epoch Converter
Convert epoch seconds, ms & microseconds
Timestamp to Date
Convert Unix timestamps into readable dates
Date to Timestamp
Convert dates into Unix timestamps
Business Days Calculator
Count business days & exclude holidays
Timezone Difference
Compare timezones & find overlap hours
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Discovery Pages
About DuskTools
DuskTools is a collection of 156 free online developer tools that run entirely in your browser. No signup, no tracking, no server-side processing — your data stays private. Use our JSON formatter, regex tester, color tools, encoders, and calculators to speed up your workflow. All tools are built for developers, by developers.