Developer Sandbox

Free, privacy-first developer utilities. Most tools run entirely in your browser. AI tools are powered by server-side API keys.

65 tools found
PDF Compressor
Losslessly compress PDF files entirely in your browser. No server uploads.
Image Resizer
Batch resize and heavily optimize PNG/JPEG/WEBP assets.
Color Palette Generator
Generate accessible, UI-ready color scales instantly.
JSON Formatter
Validate, format, and minify complex JSON structures.
Base64 Encoder
Convert string or file data to Base64 fast.
CSS Generators
Visual tools for gradients, shadows, and borders.
Resume Review
Upload your resume and get structured AI feedback. Uses free AI models.
Prompt Enhancer
Transform basic prompts into detailed, structured instructions.
Project Cost Estimator
Get an instant rough estimate for your web or AI project.
JWT Decoder & Debugger
Decode JSON Web Tokens offline to view headers, payloads, and signatures.
RegEx Tester & Builder
Visual tool to build and test regular expressions instantly.
Difference (Diff) Viewer
Visual comparison of changes between two code blocks.
URL / URI Encoder & Decoder
Convert encoded URLs or query strings into readable text.
Favicon Generator
Generate perfectly sized .ico and .png favicons instantly.
CRON Expression Builder
Build CRON schedules and preview execution times.
Hash & HMAC Generator
Local calculation of MD5, SHA hashes, and UUID generation.
SQL Formatter
Convert messy SQL queries into beautifully indented code.
AI Background Remover
Perfectly strip the background from any image securely in the browser.
Password Generator & Checker
Generate highly secure passwords and check their entropy.
PDF Merger & Splitter
Combine multiple PDFs or extract specific pages on your device.
QR Code Generator
Generate customizable QR codes for URLs, Wi-Fi, or text.
Markdown to HTML Converter
Write Markdown with a live preview and compile to HTML.
AI Cover Letter Generator
Paste a job description and resume to generate a cover letter.
Explain This Code
Paste confusing legacy code and get a plain-English explanation.
Grammar & Tone Polisher
Rewrite emails or messages to sound more professional.
Word & Character Counter
See instant word, character, and sentence counts plus reading time.
Case Converter
Convert text between UPPERCASE, camelCase, snake_case, and kebab-case.
Receipt / Expense Scanner
Extract totals, dates, and vendors from receipt images using AI.
Timezone Meeting Planner
Visually slide a timeline to see multiple timezones simultaneously.
Color Blindness Simulator
Simulate Protanopia and Deuteranopia to check UI accessibility.
Dummy Data Generator
Generate realistic fake user data in JSON/CSV format.
SVG Optimizer
Get clean, minified, React-ready SVG code.
Environment (.env) Validator
See missing or malformed environment variables instantly.
Aspect Ratio Calculator
Calculate exact pixel dimensions for any aspect ratio.
Bcrypt Hash & Verifier
Generate secure bcrypt hashes or test password matches.
Meta Tag / SEO Generator
Generate precise meta tags for social media sharing.
OG Preview
Preview how your site appears on social media.
Freelance Rate Calculator
Calculate the exact hourly rate you need for income goals.
Compound Interest Calculator
Graphical chart showing investment growth over time.
YAML-JSON Converter
Convert between YAML and JSON formats seamlessly.
UUID Generator
Generate UUIDs v1, v4, v5 with validation support.
Timestamp Converter
Unix timestamp to Human date conversion made simple.
HTML Encoder
HTML entities encode/decode utility.
Lorem Ipsum Generator
Generate placeholder text for designs and mockups.
Color Converter
HEX, RGB, HSL, OKLCH color converter.
XML-JSON Converter
Convert between XML and JSON formats.
CSS Minifier
Minify CSS stylesheets for better performance.
JS Minifier
Minify JavaScript code for production.
JSON Diff
Compare two JSON objects and see the differences.
Query String Builder
Build and parse URL query strings easily.
Image to Base64
Convert images to base64 encoded strings.
Unit Converter
PX to REM, KB to MB, and other unit conversions.
Percentage Calculator
Quick percentage calculations for any use case.
HTTP Status Codes
Quick reference for HTTP status codes.
MIME Types
MIME type lookup reference.
Git Cheatsheet
Git command reference for everyday use.
API Tester
Simple HTTP client for testing APIs.
SSL Decoder
Decode SSL certificates and view details.
JWT Generator
Create JWT tokens with custom payloads.
Credit Card Generator
Generate test credit card numbers.
User Agent Parser
Parse browser/OS info from user agent strings.
IBAN Validator
Validate IBAN numbers for banking.
Emoji Picker
Copy emojis with their shortcodes.
Password Strength
Check password strength and security.
Analytics Dashboard
View your tool usage statistics. Privacy-first, local storage only.