Developer Tools
Handy utilities for programmers and web designers: format and validate JSON, convert JSON to CSV, minify CSS, beautify HTML and JavaScript, format SQL, decode JWTs, build cron schedules, convert Markdown to HTML, encode and decode Base64 and URLs, generate UUIDs and hashes, test regular expressions with live highlighting and convert colors between HEX, RGB and HSL. Everything runs locally, so your data stays with you.
14 free tools. Tap any card to open it. No sign-up needed.
Pick the right developer tool
- APIs and config: the JSON formatter and validator pretty-prints JSON and points to the exact error. See how to fix invalid JSON.
- Encoding: Base64 and URL encoding make data safe to put in text, emails and URLs. Read what Base64 is.
- IDs and checksums: the UUID generator and hash generator create random IDs and fingerprints of text.
- Front end: the regex tester and colour converter help with patterns and HEX, RGB and HSL values.
Security notes
Encoding is not encryption: Base64 and URL encoding can be reversed by anyone. Everything on this page runs locally in your browser and nothing is sent to a server, but you should still avoid pasting production secrets or private keys into any website. Our developer guides link to the official specifications for deeper reading.
Guides and articles
- What Is Base64 Encoding? How It Works, With ExamplesBase64 explained simply: how it turns bytes into text, a step-by-step example, why output grows by a third, padding, URL-safe Base64 and when not to use it.
- How to Fix Invalid JSON: 10 Common Errors and Their FixesFix Unexpected token and other JSON errors: trailing commas, single quotes, comments, unquoted keys, bad escapes and more, with before-and-after examples.
- What Is a UUID? Versions, Format and When to Use OneUUIDs explained: the 8-4-4-4-12 format, how version 4 and version 7 differ, how unlikely collisions are, UUID vs GUID, and how to generate them in code.
- How to Convert HEX to RGB (and RGB to HEX) by HandConvert HEX colour codes to RGB and back step by step, including shorthand and 8-digit alpha codes, with worked examples, CSS tips and a contrast check.
- Unit Conversion Cheat Sheet: Metric and ImperialHandy conversion factors for length, weight, volume and temperature, plus tips for converting without mistakes.
- How to Create Strong Passwords (and Remember Them)What makes a password strong, why length beats complexity, how passphrases and password managers help, and what to avoid.
