50+ Free Online Developer Tools That Run 100% in Your Browser

Noureddine — Sun, 28 Jun 2026 15:25:47 +0000

Every developer has been there: you need to quickly format some JSON, generate a UUID, or convert a color from hex to HSL. You Google for a tool, find one, paste your data — and wonder: is this uploading my data to some server somewhere?

Most online dev tools send your data to a backend. That's a problem if you're working with API keys, JWTs, internal configs, or customer data.

All the tools below run entirely in your browser — client-side JavaScript, no server uploads. Your data never leaves your computer.

There are no accounts, no sign-ups, and no usage limits. Just open and use.

JSON Tools

JSON Formatter & Validator — Format, validate, and beautify JSON with syntax highlighting and error detection
JSON to CSV Converter — Convert JSON arrays to Excel-ready CSV with BOM and nested object flattening
YAML to JSON Converter — Convert between YAML and JSON with live preview
XML Formatter — Format, validate, and beautify XML documents
SQL Formatter — Beautify SQL queries with customizable indentation

Encoding & Crypto

Base64 Encoder / Decoder — Encode and decode text/files to/from Base64
URL Encoder / Decoder — Encode and decode URLs and query parameters
HTML Entities Encoder — Convert special characters to HTML entities for safe rendering
Hash Generator — Generate MD5, SHA-1, SHA-256, SHA-512 hashes
JWT Decoder — Decode and inspect JWT token header, payload, and signature
JWT Expiration Checker — Check token expiration and inspect claims

Generators

Password Generator — Cryptographically secure random passwords with customizable options
UUID Generator — Generate UUID v4 identifiers, bulk mode up to 100 at a time
UUID v7 Generator — Time-ordered UUID v7 identifiers for database-friendly keys
Lorem Ipsum Generator — Generate placeholder text in paragraphs, sentences, or words
QR Code Generator — Create QR codes from text/URLs, download as SVG
Wi-Fi QR Code Generator — QR code for instant Wi-Fi network access
Secure WPA2 Password Generator — Router-friendly passwords without ambiguous characters

Conversion Tools

Color Converter — Convert between HEX, RGB, HSL, and named CSS colors
Case Converter — Convert between camelCase, snake_case, kebab-case, and more
CSS px to rem Converter — Convert pixel values to rem units with reference table
Image Converter — Convert images between PNG, JPEG, WebP, GIF in your browser

Text & Markdown

Markdown Preview — Write and preview Markdown with live HTML rendering
Text Diff Checker — Compare two texts side-by-side highlighting changes
Regex Tester — Test regular expressions with match highlighting and group capture
Word & Character Counter — Count words, characters, sentences, and reading time
Remove Duplicate Lines — Deduplicate and sort text lines

Validators

Kubernetes YAML Validator — Validate K8s manifests for pods, deployments, services
Docker Compose Validator — Validate docker-compose.yml files
GitHub Actions Validator — Validate workflow YAML syntax and structure

Why I Built This

I got tired of bookmarking 50 different utility sites. I wanted one place where everything works offline-capable, client-side only, with no tracking. The entire site is built with Astro and TypeScript — check it out on GitHub.

Quick Tips

Bookmark WebUtil — one shortcut for all your daily tools
All tools are PWA-ready — add to your home screen for offline access
No data leaves your browser — safe for API keys, tokens, and internal data

DEV Community: Noureddine