Developer Utilities Online
Free online developer utilities — decode JWTs, test regex patterns, generate hashes, convert colors, preview Markdown and compare text. Everything runs locally in your browser.
Debug and decode JWT tokens — inspect header, payload claims, expiry status and algorithm. Your token never leaves your browser.
Test JavaScript regex patterns with live match highlighting, group captures and replace mode. Includes a built-in regex cheat sheet.
Generate MD5, SHA-1, SHA-256 and SHA-512 hashes from text or files. Use for checksums, file integrity and password hashing.
Convert colors between HEX, RGB, HSL, HSV and CMYK with a visual color picker. Includes a WCAG contrast ratio checker.
Write Markdown and preview rendered HTML in real time. Supports GitHub Flavored Markdown — perfect for README files and docs.
Compare two texts, documents or code snippets and highlight every addition and deletion line by line.
About These Developer Utilities
These utilities cover the everyday debugging and inspection tasks developers face — decoding a JWT during auth debugging, testing a regex pattern before deploying it, generating a checksum to verify a file download, or checking color contrast for accessibility compliance.
Every tool processes data locally in your browser. No tokens, hashes, regex patterns or file contents are ever sent to a server. Safe to use with production secrets and sensitive data.
Frequently Asked Questions
Can I use the JWT Decoder with production tokens?
Yes, it is safe. The JWT Decoder runs entirely in your browser — your token is never sent to any server. It only decodes the payload; it does not verify the signature.
Which hash algorithm should I use for checksums?
SHA-256 is the recommended standard for file integrity checksums. Use MD5 only for non-security purposes (like cache keys) as it is no longer considered cryptographically secure.
Does the Regex Tester support Python or PHP regex?
The Regex Tester uses JavaScript's built-in RegExp engine. Most common patterns work across languages, but syntax for some advanced features (like lookbehinds or named groups) may differ slightly.
Can I preview GitHub README files with the Markdown tool?
Yes. The Markdown Preview tool supports GitHub Flavored Markdown (GFM) including tables, task lists, strikethrough and fenced code blocks — the same spec GitHub uses to render README files.
What is the WCAG contrast checker in the Color Converter for?
WCAG (Web Content Accessibility Guidelines) defines minimum contrast ratios between text and background colors. A ratio of at least 4.5:1 is required for normal text to meet AA compliance.