Developer Tools
Small daily tools for developers: JSON formatter and validator, Base64 and URL encoding, UUID generator, SHA hashes, JWT decoder, regex tester, Unix timestamp converter and color converter. Nothing to install — just open and use.
JSON Formatter Paste JSON to validate and pretty-print it instantly, or minify it into a single line. If it is invalid, you get the exact line and column plus a plain-English explanation of what is wrong. Base64 Encode and Decode Turn text into Base64 or decode a Base64 string back to readable text. Everything is handled as UTF-8, so accented letters, emoji and non-Latin scripts come back exactly as they went in. Color Converter Convert any CSS color between HEX, RGB, HSL and OKLCH, and see right away whether white or black text on it passes WCAG contrast. Works with transparency too. Roman Numeral Converter Type a number to get its Roman numeral, or type a Roman numeral to get the number. Each result is broken into parts, so you can see how it is built. Unix Timestamp Converter Check the current Unix timestamp, or convert between epoch time and human-readable dates. Seconds and milliseconds are detected automatically, and every result is shown in your local time, UTC and ISO 8601. URL Encode and Decode Percent-encode text for use in a URL, or decode %XX sequences back into readable text. Paste a full link below to break it into its scheme, host, path and decoded query parameters. Hash Generator Calculate MD5, SHA-1, SHA-256, SHA-384 and SHA-512 for any text or file in one go. Paste a published checksum to confirm that a download is intact and untampered. Number Base Converter Type a whole number in binary, octal, decimal, hex or any base from 2 to 36 and every other base updates instantly. Big numbers stay exact, and the two’s complement panel shows how the value is stored in 8 to 64 bits. Regex Tester Type a pattern and some text to see every match highlighted, what each capture group grabbed, and what a replacement would produce. Runs on the JavaScript regex engine in your browser. UUID Generator Generate up to 100 UUIDs at once, either random version 4 or time-ordered version 7. Paste an existing UUID below to see which version it is and, for v1, v6 and v7, when it was created. JWT Decoder Paste a JWT to see its header and payload as formatted JSON. Time claims such as exp and iat are converted to dates in your time zone, and a live countdown tells you whether the token has expired. Markdown Preview Write Markdown on the left and see it rendered on the right as you type. Supports GitHub Flavored Markdown, and lets you copy the HTML or download the result as a file. HTML Entity Encoder / Decoder Escape text so it displays safely inside HTML, or turn entities like < & © back into normal characters. Includes a cheat sheet of the most common HTML entities.