Free Online Developer Tools

Free online developer tools eliminate hours of repetitive work. Whether you need to format and validate JSON before sending it to an API, encode binary data as Base64 for safe HTTP transmission, or decode a JWT token to inspect its claims without a local environment, every common dev workflow is covered.

Each tool runs entirely in your browser using client-side JavaScript. Your code, tokens, and sensitive credentials never leave your device — making them safe to use with production data and API secrets.

The collection includes a JSON Formatter with syntax highlighting and validation, a Base64 Encoder/Decoder for text and files, a URL Encoder/Decoder for percent-encoding, a UUID Generator with v4 and v7 support, a JWT Decoder for inspecting token headers and payloads, and a Regex Tester with live match highlighting and group capture display.

For code optimization, the HTML Minifier, CSS Minifier, and JavaScript Minifier strip whitespace and comments from your production assets — and the Code Beautifier reverses that, restoring readable indentation to minified HTML, CSS, and JavaScript when you need to debug a bundle or read a vendor stylesheet. For data format conversion, the JSON-to-CSV Converter, XML-to-JSON Converter, YAML-to-JSON Converter, and CSV Viewer handle every modern data interchange format. The Base64 Image Encoder/Decoder generates data URIs for embedding images directly in HTML and CSS.

The SQL Formatter turns a one-line ORM dump back into something readable, with nineteen dialects so vendor syntax from T-SQL, PostgreSQL, or BigQuery parses correctly rather than being rejected. The HEX to RGB Converter handles the other constant chore — translating a colour between HEX, RGB, HSL, HSV, and CMYK, with alpha support and a built-in WCAG contrast check so you can tell at a glance whether white or black text will be readable on it.

Seven more cover the jobs that come up mid-task. JSON to TypeScript infers interfaces, Go structs or Python dataclasses from a sample, marking fields optional when they are missing from some array items. JSON Diff compares two documents structurally so key order and formatting are ignored entirely. The XML Formatter re-indents without parsing and rebuilding, so comments, CDATA and attribute order survive. The Cron Expression Generator translates a schedule into plain English and previews the next five run times, which catches misread schedules immediately. The Markdown Editor gives a live sanitised preview, the Markdown and HTML Converter goes both ways, and the gitignore Generator assembles a deduplicated file from language, framework, editor and OS templates.

Rounding out the set are the everyday debugging utilities: the Text Diff Checker highlights exactly what changed between two versions of a file or response body, the Unix Timestamp Converter translates epoch values into human-readable dates in either direction, the Number Base Converter moves values between binary, octal, decimal, and hexadecimal, and the HTML Entity Encoder/Decoder escapes markup safely for templates and documentation.