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Developer sandbox & tooling

High-Performance Developer Tools & Utilities

65+ production-grade utilities engineered for developer velocity and zero-trust privacy. All crypto, parsing, and formatting run entirely client-side in your browser tab.
65+ Tools
Production Utilities
Formatters, decoders, crypto, converters & AI
100% In-Browser
Zero Data Logging
Transformed in client V8 memory, zero telemetry
Web Crypto
Hardware Entropy
SubtleCrypto CSPRNG & native browser runtimes
Sub-5ms
Execution Latency
Zero-roundtrip local parsing & formatting
ZERO-KNOWLEDGE BROWSER SANDBOX

Privacy-First Client Architecture

Transformations, hash computations, and formatters execute strictly in your browser's local V8 thread. No input payloads, keys, or tokens ever touch an external server. Hardware-backed cryptographic entropy is sourced directly from crypto.subtle.

Production Systems ↗

Flagship Daily Drivers

[CURATED DEVELOPER ESSENTIALS]
Fast, zero-upload local runtimes
Security

JWT Decoder & Debugger

Decode, verify, and inspect JSON Web Tokens locally with zero network leaks.

RS256/HS256 claim inspection & expiry validation
Web CryptoLaunch
Formatters

JSON Formatter & Validator

Instant beautification, syntax validation, and minification with zero payload limits.

Fast AST validation & tree structure navigation
Client SandboxLaunch
Generators

Password & Entropy Generator

CSPRNG cryptographic entropy with Shannon bit-strength analysis and bcrypt hashing.

Hardware-backed window.crypto.getRandomValues
Web CryptoLaunch
Utilities

API Tester & Mock Sandbox

Execute REST/HTTP requests, inspect headers, and measure latency directly in your browser.

Payload staging, timing breakdown & response headers
Client SandboxLaunch
Utilities

PDF Compressor & Optimizer

Client-side PDF downsampling and image compression without uploading files anywhere.

Off-thread Web Worker canvas re-encoding
Worker / CanvasLaunch
Utilities

Difference (Diff) Viewer

Side-by-side and unified Myers diff comparison for code snippets, JSON, and text.

Line-by-line & character-level inline syntax diffing
Client SandboxLaunch
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Runtime:
Showing 65 of 65 utilities
Utilities

PDF Compressor

Losslessly compress PDF files entirely in your browser. No server uploads.

#pdf#compress#optimize
Worker / Canvas
Open
Utilities

Image Resizer

Batch resize and heavily optimize PNG/JPEG/WEBP assets.

#image#resize#png
Worker / Canvas
Open
Generators

Color Palette Generator

Generate accessible, UI-ready color scales instantly.

#color#palette#design
Worker / Canvas
Open
Formatters

JSON Formatter

Validate, format, and minify complex JSON structures.

#json#format#validate
Client Sandbox
Open
Encoders

Base64 Encoder

Convert string or file data to Base64 fast.

#base64#encode#decode
Client Sandbox
Open
Utilities

CSS Generators

Visual tools for gradients, shadows, and borders.

#css#gradient#shadow
Client Sandbox
Open
Utilities

Resume Review

Upload your resume and get structured AI feedback. Uses free AI models.

#resume#cv#review
AI Engine
Open
Utilities

Prompt Enhancer

Transform basic prompts into detailed, structured instructions.

#prompt#ai#llm
AI Engine
Open
Utilities

Project Cost Estimator

Get an instant rough estimate for your web or AI project.

#cost#estimate#pricing
Client Sandbox
Open
Security

JWT Decoder & Debugger

Decode JSON Web Tokens offline to view headers, payloads, and signatures.

#jwt#token#decode
Web Crypto
Open
Utilities

RegEx Tester & Builder

Visual tool to build and test regular expressions instantly.

#regex#regexp#pattern
Client Sandbox
Open
Utilities

Difference (Diff) Viewer

Visual comparison of changes between two code blocks.

#diff#compare#git
Client Sandbox
Open
Encoders

URL / URI Encoder & Decoder

Convert encoded URLs or query strings into readable text.

#url#uri#encode
Client Sandbox
Open
Generators

Favicon Generator

Generate perfectly sized .ico and .png favicons instantly.

#favicon#icon#browser
Worker / Canvas
Open
Generators

CRON Expression Builder

Build CRON schedules and preview execution times.

#cron#schedule#job
Client Sandbox
Open
Security

Hash & HMAC Generator

Local calculation of MD5, SHA hashes, and UUID generation.

#hash#sha#md5
Web Crypto
Open
Formatters

SQL Formatter

Convert messy SQL queries into beautifully indented code.

#sql#format#database
Client Sandbox
Open
Utilities

AI Background Remover

Perfectly strip the background from any image securely in the browser.

#image#background#remove
AI Engine
Open
Security

Password Generator & Checker

Generate highly secure passwords and check their entropy.

#password#generate#security
Web Crypto
Open
Utilities

PDF Merger & Splitter

Combine multiple PDFs or extract specific pages on your device.

#pdf#merge#split
Worker / Canvas
Open
Generators

QR Code Generator

Generate customizable QR codes for URLs, Wi-Fi, or text.

#qr#code#generator
Client Sandbox
Open
Formatters

Markdown to HTML Converter

Write Markdown with a live preview and compile to HTML.

#markdown#html#convert
Client Sandbox
Open
Generators

AI Cover Letter Generator

Paste a job description and resume to generate a cover letter.

#cover letter#resume#job
AI Engine
Open
Utilities

Explain This Code

Paste confusing legacy code and get a plain-English explanation.

#code#explain#legacy
AI Engine
Open
Utilities

Grammar & Tone Polisher

Rewrite emails or messages to sound more professional.

#grammar#tone#writing
AI Engine
Open
Utilities

Word & Character Counter

See instant word, character, and sentence counts plus reading time.

#word count#character count#reading time
Client Sandbox
Open
Converters

Case Converter

Convert text between UPPERCASE, camelCase, snake_case, and kebab-case.

#case#convert#camelcase
Client Sandbox
Open
Utilities

Receipt / Expense Scanner

Extract totals, dates, and vendors from receipt images using AI.

#receipt#expense#ocr
Client Sandbox
Open
Utilities

Timezone Meeting Planner

Visually slide a timeline to see multiple timezones simultaneously.

#timezone#meeting#scheduler
Client Sandbox
Open
Utilities

Color Blindness Simulator

Simulate Protanopia and Deuteranopia to check UI accessibility.

#color blindness#accessibility#a11y
Worker / Canvas
Open
Generators

Dummy Data Generator

Generate realistic fake user data in JSON/CSV format.

#dummy data#mock#json
Client Sandbox
Open
Utilities

SVG Optimizer

Get clean, minified, React-ready SVG code.

#svg#optimize#minify
Worker / Canvas
Open
Utilities

Environment (.env) Validator

See missing or malformed environment variables instantly.

#env#environment#config
Client Sandbox
Open
Utilities

Aspect Ratio Calculator

Calculate exact pixel dimensions for any aspect ratio.

#aspect ratio#calculate#dimensions
Client Sandbox
Open
Security

Bcrypt Hash & Verifier

Generate secure bcrypt hashes or test password matches.

#bcrypt#hash#password
Web Crypto
Open
Generators

Meta Tag / SEO Generator

Generate precise meta tags for social media sharing.

#meta tags#seo#social
Client Sandbox
Open
Utilities

OG Preview

Preview how your site appears on social media.

#og#open graph#preview
Client Sandbox
Open
Utilities

Freelance Rate Calculator

Calculate the exact hourly rate you need for income goals.

#freelance#rate#pricing
Client Sandbox
Open
Utilities

Compound Interest Calculator

Graphical chart showing investment growth over time.

#compound interest#investment#calculator
Client Sandbox
Open
Formatters

YAML-JSON Converter

Convert between YAML and JSON formats seamlessly.

#yaml#json#convert
Client Sandbox
Open
Generators

UUID Generator

Generate UUIDs v1, v4, v5 with validation support.

#uuid#guid#generate
Web Crypto
Open
Converters

Timestamp Converter

Unix timestamp to Human date conversion made simple.

#timestamp#unix#epoch
Client Sandbox
Open
Encoders

HTML Encoder

HTML entities encode/decode utility.

#html#encode#decode
Client Sandbox
Open
Generators

Lorem Ipsum Generator

Generate placeholder text for designs and mockups.

#lorem ipsum#placeholder#text
Client Sandbox
Open
Converters

Color Converter

HEX, RGB, HSL, OKLCH color converter.

#color#hex#rgb
Client Sandbox
Open
Formatters

XML-JSON Converter

Convert between XML and JSON formats.

#xml#json#convert
Client Sandbox
Open
Utilities

CSS Minifier

Minify CSS stylesheets for better performance.

#css#minify#compress
Client Sandbox
Open
Utilities

JS Minifier

Minify JavaScript code for production.

#javascript#minify#compress
Client Sandbox
Open
Utilities

JSON Diff

Compare two JSON objects and see the differences.

#json#diff#compare
Client Sandbox
Open
Utilities

Query String Builder

Build and parse URL query strings easily.

#query string#url#parameters
Client Sandbox
Open
Converters

Image to Base64

Convert images to base64 encoded strings.

#image#base64#convert
Worker / Canvas
Open
Converters

Unit Converter

PX to REM, KB to MB, and other unit conversions.

#unit#convert#px
Client Sandbox
Open
Utilities

Percentage Calculator

Quick percentage calculations for any use case.

#percentage#calculate#math
Client Sandbox
Open
Utilities

HTTP Status Codes

Quick reference for HTTP status codes.

#http#status code#reference
Client Sandbox
Open
Utilities

MIME Types

MIME type lookup reference.

#mime#content type#file
Client Sandbox
Open
Utilities

Git Cheatsheet

Git command reference for everyday use.

#git#cheatsheet#commands
Client Sandbox
Open
Utilities

API Tester

Simple HTTP client for testing APIs.

#api#test#http
Client Sandbox
Open
Security

SSL Decoder

Decode SSL certificates and view details.

#ssl#certificate#decode
Web Crypto
Open
Generators

JWT Generator

Create JWT tokens with custom payloads.

#jwt#generate#token
Web Crypto
Open
Security

Credit Card Generator

Generate test credit card numbers.

#credit card#generator#test
Client Sandbox
Open
Utilities

User Agent Parser

Parse browser/OS info from user agent strings.

#user agent#parser#browser
Client Sandbox
Open
Utilities

IBAN Validator

Validate IBAN numbers for banking.

#iban#validator#bank
Web Crypto
Open
Utilities

Emoji Picker

Copy emojis with their shortcodes.

#emoji#picker#unicode
Client Sandbox
Open
Security

Password Strength

Check password strength and security.

#password#strength#security
Web Crypto
Open
Utilities

Analytics Dashboard

View your tool usage statistics. Privacy-first, local storage only.

#analytics#stats#usage
Client Sandbox
Open
NEXUS TOOLING ASSISTANT

Need a Custom Script or Automated Pipeline?

Nexus AI can recommend the fastest client-side tool for your payload or generate custom CLI parsing scripts, TypeScript schemas, and regex patterns directly in real-time.

Index Taxonomy

Browse Directory by Category

Formatters ↗

JSON, SQL, CSS, and JS formatters that parse in the tab. Start with the JSON formatter if you need a privacy-first beautifier.

Encoders ↗

Base64, URL, and HTML encoding without uploading files. Pair with JWT decode when tokens are the payload.

Generators ↗

Passwords, UUIDs, hashes, and cron — generated with Web Crypto or local math, not a hosted entropy API.

Converters ↗

Timestamps, colors, YAML/JSON, and units. Convert locally when logs and design tokens disagree.

Security ↗

JWT, bcrypt, SSL, and password strength. Inspect claims and hashes without pasting secrets into a third-party debugger.

Utilities ↗

HTTP tester, regex, PDF, and the rest of the sandbox. Most tools never leave the device; AI helpers are labeled when they do.

rejisterjack

Full-stack engineer who owns production agentic systems — tenancy, tool-calling evals, and supply-chain-hardened delivery.

rejisterjack@gmail.com
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