Handy Dev ToolsFree tools for developers
JSON/YAML conversion, Base64 encode, test data generation, and more
All tools are free and require no registration
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Completely free
Runs in your browser
3 reasons to choose Handy Dev Tools
Runs entirely in your browser
Your data is never saved on our servers; everything is processed locally in your browser.
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Lightweight design with minimal loading. Launch tools instantly when you need them, without ads or distractions.
Built for real-world needs
Every tool is hand-picked by practicing engineers based on real needs from AWS operations and debugging.
Frequently used tools
JSON to YAML Conversion
Convert JSON data to YAML format. Useful for config files, CI/CD settings, and other scenarios requiring YAML. Enter text or upload a file (up to 100KB) and see real-time conversion results.
Base64 Encoder/Decoder
Base64 is an encoding scheme for representing binary data in text format. It uses 64 characters (A-Z, a-z, 0-9, +, /) to represent data. This tool allows you to encode text data to Base64 format or decode Base64 data to text. You can process data up to 5120 characters.
Test Data Generator Tool
Easily generate dummy data for development and testing. Supports 50+ data types from Japanese names, addresses, and My Number to JWT, API keys, and Lorem ipsum. Export as CSV, JSON, or SQL. Free with no registration required.
Regex Tester
Test regular expressions
QR Code Generator
Generate QR codes from text, URL, WiFi, vCard, and more. Customize and export as PNG, SVG, or PDF.
All tools
Data Format Conversion
JSON/YAML/XML conversion, formatters, encode/decode, etc.Base64 Encoder/Decoder
Base64 is an encoding scheme for representing binary data in text format. It uses 64 characters (A-Z, a-z, 0-9, +, /) to represent data. This tool allows you to encode text data to Base64 format or decode Base64 data to text. You can process data up to 5120 characters.
Markdown to HTML
Convert Markdown text to HTML
HTML to Markdown
Convert HTML text to Markdown
URL Encoder/Decoder
URL encoding/decoding tool. Encode text data to URL format or decode URL-encoded data to text. You can process data up to 5120 characters.
Unicode Escape Converter
Unicodeエスケープ（\uXXXX）と文字列を双方向に変換します
Unicode Encode/Decode
Convert between Unicode code point notation (U+, &#x, &#, 0x) and text in both directions.
SQL Formatter
SQL formatter tool. Enter SQL data in the text input field and get formatted SQL. Processes up to 5,120 characters.
SQL Splitter
SQL splitter tool. Enter a string containing multiple SQL queries in the text input field and split them into individual SQL queries.
JSON Formatter
JSON formatter tool. Enter JSON data using either text input or file upload, and get formatted JSON. Supports files up to 100KB in size.
XML Formatter
XML formatter tool. Enter XML data using either text input or file upload, and get formatted XML. Supports files up to 100KB in size.
YAML Formatter
YAML formatter tool. Enter YAML data using either text input or file upload, and get formatted YAML. Supports files up to 100KB in size.
GraphQL Formatter
GraphQL formatter tool. Format GraphQL queries and variables, check syntax. Searchable as graphql formatter, graphql format.
JSON to YAML Conversion
Convert JSON data to YAML format. Useful for config files, CI/CD settings, and other scenarios requiring YAML. Enter text or upload a file (up to 100KB) and see real-time conversion results.
YAML to JSON Conversion
Convert YAML data to JSON format. Useful for API requests and config compatibility. Enter text or upload a file (up to 100KB) and see real-time conversion results.
JSON to TOML Conversion
Convert JSON data to TOML format. Useful for config files (e.g. Cargo.toml) and tool settings. Enter text or upload a file (up to 100KB) and see real-time conversion results.
TOML to JSON Conversion
Convert TOML data to JSON format. Useful for API integration and config compatibility. Enter text or upload a file (up to 100KB) and see real-time conversion results.
HTML Entity Encode/Decode
Convert between plain text and HTML entities (< > & etc.) in real time. Encode turns special characters into entities; decode restores them. Input and output use text fields with file load and copy support.
TOML to YAML Conversion
Convert TOML data to YAML format. Useful for K8s manifests, CI configs, and other scenarios requiring YAML. Enter text or upload a file (up to 100KB) and see real-time conversion results.
YAML to TOML Conversion
Convert YAML data to TOML format. Useful for pyproject.toml and other scenarios requiring TOML. Enter text or upload a file (up to 100KB) and see real-time conversion results.
CSV to SQL INSERT Conversion
Convert CSV data to SQL INSERT statements. Choose separator (comma/tab) and table name; enter text or upload a file (up to 100KB) for real-time INSERT output.
Markdown Table Generator
Convert CSV/TSV to Markdown tables. Choose delimiter (comma/tab) and alignment (left/center/right); enter text or load a file (up to 100KB) for real-time Markdown table output. Switch between code and preview to view or copy.
JSON to XML Conversion
Convert JSON data to XML format. Useful for SOAP, RSS, config files, and other scenarios requiring XML. Enter text or upload a file (up to 100KB) and see real-time conversion results.
XML to JSON Conversion
Convert XML data to JSON format. Useful for API integration and config compatibility. Enter text or upload a file (up to 100KB) and see real-time conversion results.
Test Data & String Generators
Test data, UUID, password, QR code, hash generation, etc.UUID Generator
Generate UUIDs
ULID Generator
Generate ULIDs
Password Generator
Generate passwords
Hash Generator
Generate various hash values from text or files
Lorem Ipsum Generator
Generate dummy text
Lorem Picsum Image URL Generator
Generate placeholder image URLs
Test Data Generator Tool
Easily generate dummy data for development and testing. Supports 50+ data types from Japanese names, addresses, and My Number to JWT, API keys, and Lorem ipsum. Export as CSV, JSON, or SQL. Free with no registration required.
QR Code Generator
Generate QR codes from text, URL, WiFi, vCard, and more. Customize and export as PNG, SVG, or PDF.
AWS & Cloud Development
CloudFront, S3, RDS, IP calculator, subnet tools, etc.S3 Path Parser & Converter
Instantly parse S3 URIs (s3://...). Extract bucket names and keys, and automatically generate direct links to the management console.
IP Address Calculator
Calculate network information from CIDR notation or IP address + subnet mask
Subnet Split
Split an original network into multiple subnets
Subnet Consolidation
Consolidate multiple contiguous subnets into one larger subnet
CloudFront Signed URL Generator
Generate signed URLs for AWS CloudFront private content
RDS Connection String Generator
Generate connection strings for AWS RDS instances
Location & Maps
Coordinate conversion, GeoJSON/WKT/KML conversion, etc.Coordinate Format Converter
Convert coordinates between decimal degrees, DMS, DMM, UTM, MGRS, and Geohash. Enter one per line.
Geo Format Converter
Convert between GeoJSON, KML, WKT, GPX, TopoJSON, and Google Maps Polyline. Paste or load from file; copy the result.
Security & Authentication
JWT, Basic auth, RSA keys, password strength, card validation, etc.JWT Decoder & Parser
Decode JSON Web Tokens and view their contents. Header and Payload are displayed instantly. All processing, including signature verification, is done entirely in the browser for security.
Basic Auth
Generate .htpasswd, cURL, URL, and Authorization header from ID and password in real time.
Password Strength Analyzer
Analyze password strength in real-time. Displays detailed information such as crack time, entropy, character set size, and score. All processing is performed locally in the browser, and passwords are not sent to the server.
Credit Card Validator
Validates credit card numbers using the Luhn algorithm
RSA Key Pair Generator
Generate RSA public and private key pairs in your browser
Regex & Text Processing
Regex tester, diff, character count, case conversion, etc.Case Conversion
Convert text case formats
Romaji Conversion
Convert Japanese text to romaji
Roman Numeral Conversion
Convert between Roman numerals and Arabic numbers
Phonetic Code Conversion
Convert text to phonetic code
Character Counter
Display text character statistics
Text Diff
Visually display differences between two texts
HTML Tag Remover
Remove HTML tags from code and extract text content only
Regex Tester
Test regular expressions
Date/Time, Color & Misc
DateTime conversion, color, cron, emoji, dice, HTTP/MIME lookup, etc.Color Conversion
Convert color information
Dice Roll
Roll dice and display results
Crontab generator
Generate cron expressions
Crontab parser
Parse cron expressions
Emoji Picker
Search and copy emojis
DateTime Converter
Convert date and time representations to various date/time strings and timestamps in real-time
HTTP Status Code Search
Search HTTP status code meanings and display common error causes and solutions
Port Number Search
Look up service names by port number, or port numbers by service name.
MIME Type Lookup
Search between file extensions and MIME types
Developer Tools
User-Agent parser, URL parser, OGP checker, commit message, Base64 file, etc.Base64 File Converter
Convert between Base64 strings and files in both directions.
Image Base64 Encode/Decode
Convert between images and Base64 in both directions.
JSON to XML Conversion
Convert JSON data to XML format. Useful for SOAP, RSS, config files, and other scenarios requiring XML. Enter text or upload a file (up to 100KB) and see real-time conversion results.
XML to JSON Conversion
Convert XML data to JSON format. Useful for API integration and config compatibility. Enter text or upload a file (up to 100KB) and see real-time conversion results.
User-Agent Parser
A tool that parses User-Agent strings from HTTP request headers and extracts and displays browser, OS, and device information.
URL Parser
Parse URL and extract/display each component
OGP Checker
Fetch and display OGP and Twitter card meta for a URL and preview how it will look when shared.
Commit Message Generator
Generate Conventional Commits-style commit messages
Chmod Calculator
Convert between chmod numeric (755/2775) and symbolic (rwxr-xr-x) and copy the command.
Terminal GIF Generator
Replays pseudo-terminal output and records it as a GIF animation for download.