About JustKit
Developer utilities the way the calc family does them — fast, no signups, runs in your browser, never sends data anywhere.
Why this exists
Searching for "json formatter" or "jwt decoder" leads to a long list of results, most of which sit behind cookie banners, sign-up walls, three ads above the fold, and "AI Code Helper" upsells. The work itself takes one line of code. JustKit is the version without the funnel — open the tool, paste, copy.
Sister to JustCalc and GulfCalc. Same philosophy: bookmark-worthy tools that respect your time and data.
How it works
Every tool on JustKit runs entirely in your browser. There is no server doing the work. No tokens, JSON payloads, or hashes you generate ever leave your device. The page is a few KB of HTML and a few KB of vanilla JavaScript — it loads instantly, works offline once cached, and depends on no third-party APIs.
Privacy
We don't track you. Concretely:
- No Google Analytics, no Segment, no Hotjar, no fingerprinting.
- No advertising cookies. No "consent banner" because there's nothing to consent to.
- Your inputs are stored only in your browser's localStorage — never on a server.
- The site is served via Cloudflare, which sees standard request logs the way every website does. We don't export, sell, or analyse those logs.
- If we add Cloudflare Web Analytics, it counts page views without cookies or device fingerprints. Verify this in your browser's network tab.
Methodology
Every tool implements a standard or RFC. JSON parsing follows ECMAScript spec. JWT parsing follows RFC 7519. Base64 follows RFC 4648. Hashes are computed via the Web Crypto API (browser-native, audited). UUID v4/v7 follows RFC 9562.
For tools where there's a reference scale or recommendation (e.g. password entropy from NIST SP 800-63B), we cite it on the page.
Disclaimer
JustKit is a reference toolset. The output is accurate to the standard cited. Real-world use cases (security tokens, cryptographic keys, etc.) involve additional context a tool cannot see. For production cryptographic operations, prefer libraries audited by your security team over any client-side web tool, including this one.
Contact
Spotted a bug, want to suggest a tool, or have feedback? Email [email protected].
Sister sites
JustCalc for global utility calculators (math, money, conversions). GulfCalc for UAE-specific calculators (VAT, gratuity, mortgage, etc).