Developer Tools

32 free online tools — JSON, encoding, hashing and formatting utilities

Utilities for the small, constant chores of programming: format and validate JSON, test a regular expression, encode and decode Base64, URLs and HTML entities, generate hashes and UUIDs, decode a JWT, read a cron expression, convert between JSON, CSV, YAML and XML, minify or beautify code, and format SQL. All of them run in your browser, which matters when the data is a production token or a customer record.

Cron Expression Parser Paste a crontab line, read what it means, and see exactly when it fires next — in your zone or UTC. CSS Beautifier One rule per line, consistent indentation — minified CSS made readable again. CSS Minifier Strips comments and whitespace without ever touching what matters — calc() and strings survive. CSV to JSON Spreadsheet data in, clean JSON array out — types detected, quoting handled. Fake Data Generator Pick fields, set a row count and a seed, and get realistic test data you can reproduce exactly. HTML Beautifier Properly nested indentation for markup — including the embedded CSS and JS. HTML Entity Encoder / Decoder Turn < & " into safe entities, or decode any entity the browser knows — named, decimal or hex. HTML Minifier Collapses whitespace and strips comments — while <pre> and inline semantics stay intact. HTML to Markdown Converter Paste HTML (or rich text straight from a web page) and get clean GitHub-flavoured Markdown. HTTP Status Codes Search 70 status codes by number, class or keyword: what each one means, why you are seeing it, and what to do about it. JavaScript Beautifier Turn minified or messy JS back into something a human can read. JavaScript Minifier Actual Terser minification — compressed and mangled correctly, not regex-mangled into bugs. JSON to CSV Turn a JSON array into a spreadsheet-ready CSV, nested keys flattened. JSON to XML JSON in, well-formed XML out — attributes, repeated elements and escaping handled. JSON to YAML Valid JSON in, clean readable YAML out — config files without the bracket noise. JWT Decoder Header, payload, expiry status and HMAC verification — the token never leaves your device. Markdown to HTML Converter GitHub-flavoured Markdown in, rendered preview and copy-ready HTML out. Nothing leaves your browser. Number Base Converter Type in any field and the rest update — exact at any size, with two's complement for negatives. Regex Tester Matches highlighted as you type, with capture groups and a replacement preview. SQL Formatter Paste a one-line query and get it indented and readable — MySQL, PostgreSQL, SQL Server, Oracle, SQLite, BigQuery and more. Or squash it back to one line. Text to Binary Converter Real UTF-8 bytes in, correctly padded codes out — and back again, separators or not. User Agent Parser See your browser's user-agent string and decode any UA into browser, version, engine, OS and device — with the caveats modern browsers force on it. XML to JSON Legacy XML in, workable JSON out — attributes and repeated elements mapped predictably. YAML to JSON Config-file YAML in, strict JSON out — and an instant validity check for free. JSON Formatter Format, validate and minify JSON with error messages that point at the exact line. Base64 Encode / Decode Convert text or files to Base64 and back, with full Unicode and URL-safe support. Diff Checker Find every added, removed and changed line between two blocks of text. 🖥 URL Encode / Decode Encode or decode URLs and query strings, with a full breakdown of every URL part. Hash Generator Generate SHA-1, SHA-256, SHA-384 and SHA-512 hashes from text or any file. UUID Generator Generate cryptographically random UUIDs in bulk, in any format you need. Timestamp Converter Convert Unix timestamps to human dates and back, in seconds, milliseconds or microseconds. Lorem Ipsum Generator Generate placeholder paragraphs, sentences, words or list items in three flavours.

Grouped by job

Data formats — JSON formatter, CSV ↔ JSON, YAML and XML converters, SQL formatter.
Encoding — Base64, URL, HTML entities, text to binary/hex, number bases.
Identifiers and secrets — hashes (MD5 to SHA-512), UUIDs, JWT decoder with real signature verification.
Text and code — regex tester, diff checker, minifiers and beautifiers for JS, CSS and HTML, Markdown ↔ HTML.
Ops — cron parser, HTTP status codes, user-agent parser, fake data generator.

Why "runs in your browser" is the whole point

A JWT, a database row, an API response — the things developers paste into online tools are frequently things that should not leave the machine. Every tool on this page processes in the browser: open the network tab and watch nothing go out. Where a real library is needed (a JavaScript minifier that does not break code, an SQL parser that understands eleven dialects), it is downloaded once and runs locally.

Correctness over convenience

Several tools here exist because the quick version is wrong: a regex "minifier" that mangles JavaScript, a Base64 decoder that corrupts UTF-8, a number converter that silently rounds past 2^53, a JWT "verifier" that only decodes. Each of these implements the real thing and says what it does not do.