100% Free & Private — Zero Server Uploads

Free Online Developer Tools

Fast, private developer utilities for formatting JSON, converting data, decoding tokens, debugging regex, and calculating cryptographic hashes.

JSON Formatter & Validator

Beautify, inspect, validate, and minify JSON with collapsible tree view.

Use JSON Formatter & Validator →

CSV to JSON Converter

Convert tabular CSV spreadsheets to JSON arrays and vice versa.

Use CSV to JSON Converter →

YAML to JSON Converter

Convert Kubernetes and Docker Compose YAML configs to/from JSON.

Use YAML to JSON Converter →

Base64 Encoder & Decoder

Encode and decode text and binary strings to/from Base64.

Use Base64 Encoder & Decoder →

Calculate MD5, SHA-1, SHA-256, and SHA-512 cryptographic checksums.

Use Hash Generator →

Decode and inspect JSON Web Token headers, claims, and expiry dates.

Use JWT Decoder →

Test and debug regular expressions with real-time match highlighting.

Use Regex Tester →

URL Encoder & Decoder

Percent-encode and decode URL query parameters and special characters.

Use URL Encoder & Decoder →

HTML Entity Encoder

Escape HTML entities (<, >, &) or decode back to characters.

Use HTML Entity Encoder →

CSS Code Generator

Visually generate CSS box shadows, gradients, and border radius.

Use CSS Code Generator →

Bulk generate cryptographically secure RFC4122 v4 UUIDs and GUIDs.

Use UUID Generator →

Cron Expression Generator

Build, parse, and validate crontab schedules with human explanations.

Use Cron Expression Generator →

Unix Timestamp Converter

Convert epoch timestamps (seconds/ms) to human dates and vice versa.

Use Unix Timestamp Converter →

Compare two text files or code snippets with side-by-side highlighting.

Use Diff Checker →

Minify HTML, CSS, and JavaScript to optimize web asset performance.

Use Minify Code →

JavaScript Keycode Finder

Inspect keyboard event.keyCode, event.key, and code values instantly.

Use JavaScript Keycode Finder →

HTML to Markdown

Convert web articles and HTML markup into clean GitHub Markdown.

Use HTML to Markdown →

Markdown to HTML

Render Markdown files into semantic, syntax-highlighted HTML5 code.

Use Markdown to HTML →

Clean up and minify SVG vector files by removing redundant metadata.

Use SVG Optimizer →

Bcrypt Hash Tool

Generate and verify Bcrypt password hashes with custom salt rounds.

Use Bcrypt Hash Tool →

Frequently Asked Questions

Is it safe to paste confidential API keys, JWT tokens, and production JSON?

Yes! All developer tools run 100% locally in your web browser. Neither your tokens, JSON payloads, nor database records are ever logged or sent across the network.

Can I use these developer tools offline?

Yes! Once loaded, the tools operate entirely offline without requiring an active internet connection.

Why Zaeyon?

Private, free, and browser-based — no account, no uploads, no compromises.

Zero Uploads

Your files never leave your device. All processing happens locally in your browser memory — nothing is sent to any server.

100% Free Forever

No subscriptions, no hidden fees, no daily limits. Every tool on Zaeyon is permanently free to use without an account.

Instant & Powerful

Powered by WebAssembly — the same low-level technology used in native apps — so processing is fast even for large files.

Works Offline

Once the page loads, the WebAssembly engine runs entirely on your device. No internet connection needed to process files.

Works Everywhere

No software installation required. Runs directly in your browser on Windows, Mac, Linux, iOS, and Android.