Is it safe to paste my JWT token into an online decoder?

KappaKit runs entirely in your browser with zero server requests. Your JWT token never leaves your machine. You can verify this by opening the browser's Network tab while using the tool — no outbound requests are made.

How do I generate a UUID v4?

Click the UUID Generator tab in KappaKit and hit Generate. The tool uses crypto.getRandomValues() for cryptographically secure random UUIDs. You can generate up to 100 UUIDs at once and copy them with one click.

Developer Toolkit

Seven essential tools in one page. No signups, no tracking, runs entirely in your browser.

Built by Michael Lip

Base64 Encode / Decode

Text

Result

JWT Decoder

Paste JWT Token

Hash Generator

Input Text

UUID v4 Generator

Count (1-100)

Regex Tester

Pattern

g i m

Test String

Matches

URL Encoder / Decoder

Input

Result

Color Converter

HEX

RGB

HSL

Last updated: April 6, 2026

Frequently Asked Questions

How do I encode text to Base64 online?

Paste your text into the KappaKit Base64 tool and click Encode. The developer toolkit converts your input to Base64 using the browser's native btoa() function with full Unicode support. No data is sent to any server — everything runs client-side.

How do I decode a JWT token without sending it to a server?

Use the JWT Decoder tab in KappaKit. Paste your token and it splits the three parts (header, payload, signature), Base64URL-decodes them, and displays the JSON contents including expiration time and claims. Your token never leaves your browser.

What hash algorithms does KappaKit support?

KappaKit generates MD5, SHA-1, and SHA-256 hashes simultaneously from any input text. SHA-1 and SHA-256 use the Web Crypto API for hardware-accelerated speed. MD5 uses a JavaScript implementation since the Web Crypto API deliberately excludes it.

Is it safe to paste sensitive data into KappaKit?

Yes. KappaKit is a fully client-side developer toolkit — no data ever leaves your browser. There are zero network requests, no cookies, and no tracking pixels. You can verify this by checking the Network tab in your browser's dev tools.

How does the UUID v4 generator work?

KappaKit uses crypto.getRandomValues() to generate cryptographically secure random UUIDs following the RFC 4122 v4 specification. This is safer than Math.random()-based generators. You can generate up to 100 UUIDs at once and copy them all with one click.

Can I test regular expressions with different flags?

Yes. The regex tester lets you toggle global (g), case-insensitive (i), and multiline (m) flags independently. It highlights all matches in real-time and shows a total match count, making it easy to debug complex patterns before using them in your code.

How KappaKit Works

KappaKit is a free, browser-based developer toolkit that brings seven essential encoding, decoding, and conversion tools into a single page. Instead of juggling bookmarks across a dozen different utility sites, you open one URL and get instant access to Base64 encoding, JWT decoding, cryptographic hashing, UUID generation, regex testing, URL encoding, and color conversion. Every operation executes entirely in your browser using native Web APIs — there are no server calls, no user accounts, and no data collection of any kind.

The toolkit is built with static HTML, CSS, and vanilla JavaScript. There are no frameworks, no build tools, and no third-party dependencies. This means the page loads in under a second on any connection and works offline once cached. The Base64 encoder handles full Unicode text using the TextEncoder API, the hash generator leverages the Web Crypto API for hardware-accelerated SHA-256 computation, and the UUID generator uses crypto.getRandomValues() for true cryptographic randomness.

Each tool is designed to solve a specific problem that developers encounter daily. The JWT decoder parses the three-part token structure and displays the header, payload, and expiration status — making it invaluable for debugging authentication issues. The regex tester provides real-time match highlighting with flag toggles, so you can iterate on patterns without switching contexts. The color converter handles instant bidirectional conversion between HEX, RGB, and HSL formats with a live preview swatch.

Features

KappaKit includes a Base64 encoder and decoder with full Unicode support, a JWT token decoder that parses headers, payloads, and expiration claims, a hash generator producing MD5, SHA-1, and SHA-256 digests simultaneously, a UUID v4 generator with bulk generation up to 100 at once, a regex tester with global, case-insensitive, and multiline flag toggles, a URL encoder and decoder for percent-encoding, and a color converter supporting HEX, RGB, and HSL formats with a live preview swatch. All results include one-click copy buttons for fast workflow integration.

Who Uses This

KappaKit is built for software developers, DevOps engineers, QA testers, and security researchers who need quick access to encoding and conversion tools during their daily workflow. Frontend developers use the Base64 and color converter tools regularly. Backend engineers rely on the JWT decoder and hash generator for API debugging. DevOps teams use the UUID generator and URL encoder when working with infrastructure configuration. If you work with timestamps and cron schedules, check out EpochPilot for epoch conversion and timezone tools. For machine learning work involving matrix operations, ML3X provides a step-by-step matrix calculator. Security professionals who need to verify API tokens can combine the JWT decoder with the hash generator for thorough token inspection.

Privacy

Everything in KappaKit runs locally in your browser. No data is transmitted to any server — not your JWT tokens, not your hashed text, not your regex patterns. The entire site is static files served from GitHub Pages with Cloudflare CDN. The source code is open and available on GitHub, so you can inspect exactly what runs on your machine. There are no cookies, no analytics scripts, and no tracking pixels.

Contact

KappaKit is built and maintained by Michael Lip. For questions or feedback, email michael@zovo.one or visit the project on GitHub.