Developer Tools
24 free developer utilities, all running entirely in your browser. No uploads, no accounts.
JSON Formatter
Validate, format, minify, and explore JSON. Syntax highlighting, error detection, and tree view.
HTML Beautifier
Format messy HTML with proper indentation. Also minifies HTML for production.
CSS Formatter
Prettify or minify CSS. Auto-prefix properties, sort alphabetically.
SQL Formatter
Format SQL queries with keyword casing, indentation, and clause alignment.
Regex Tester
Test regular expressions with live matching, group capture, flags, and match highlighting.
Base64
Encode and decode Base64 strings and files. Supports text, binary, and data URLs.
URL Encoder/Decoder
Encode/decode URLs and query strings. Full URL or component mode.
HTML Entities
Encode HTML special characters to entities and decode them back.
JWT Decoder
Decode JSON Web Tokens and inspect header, payload, and signature.
Hash Generator
Generate SHA-256, SHA-512, SHA-1, and SHA-384 hashes using Web Crypto API.
JSON → TypeScript
Convert JSON objects to TypeScript interfaces with proper type inference.
YAML ↔ JSON
Convert between YAML and JSON formats bidirectionally.
Unix Timestamp
Convert Unix timestamps to human-readable dates and back. Supports ms and seconds.
Number Base Converter
Convert numbers between binary, octal, decimal, and hexadecimal.
Markdown Preview
Live Markdown editor with real-time HTML preview. Supports GFM syntax.
Diff Checker
Compare two text blocks and see additions, deletions, and changes highlighted.
JSON Validator
Validate and lint JSON with detailed error messages, line numbers, and type metrics breakdown.
JSON Diff Checker
Compare two JSON objects and highlight added, removed, and changed keys with a unified diff view.
JS Minifier
Minify JavaScript by removing comments and collapsing whitespace. Shows size reduction stats.
CSS Minifier
Minify CSS by removing comments, collapsing whitespace, and stripping unnecessary characters.
HTML Minifier
Minify HTML with configurable options: remove comments, collapse whitespace, minify inline CSS/JS.
HTML Preview
Live HTML+CSS preview with an iframe sandbox. Built-in templates for quick prototyping.
YAML Formatter
Format and validate YAML with normalized indentation. Interactive tree view of parsed structure.
JSON Analyzer
Deep-analyze JSON: size, depth, type distribution, top keys, longest strings, largest numbers, array stats.
How these developer tools work
Every tool in this section runs in your browser tab with no server involvement. The JSON formatter parses and re-serialises your data locally using the browser's built-in JSON engine, so invalid JSON surfaces an exact error rather than a vague failure. The diff checker compares two inputs character-by-character using a standard diff algorithm and highlights additions, deletions, and unchanged lines inline.
The JWT decoder splits the token at its period separators, base64url-decodes the header and payload, and displays them as formatted JSON. It does not make a network request to verify a signature — instead it shows you the algorithm and lets you paste a secret to run verification client-side. This means tokens containing sensitive claims stay on your device.
The regex tester evaluates your pattern against the test string in real time as you type, using the same JavaScript regex engine the browser uses. Match groups, named captures, and flags (global, multiline, case-insensitive) are all supported. The SQL formatter uses a grammar-based parser to re-indent and capitalise keywords according to standard SQL style, without connecting to any database.
Frequently Asked Questions
- Do I need to install Node.js or anything else?
- Nothing. Every dev tool runs in your browser: JSON formatter, YAML converter, regex tester, hash generator, all of it. It's just JavaScript running locally.
- Is it safe to paste sensitive code here?
- Your input never leaves your browser, so technically yes: there's no server receiving it. That said, the sensible habit with anything genuinely sensitive is to test with anonymized data regardless of where you're running it.
- What formats and languages are covered?
- JSON, YAML, SQL, XML, HTML, CSS, JavaScript, TypeScript, Markdown, Base64, JWT, regex, and more. The full list is in the grid above.
- Do these tools work offline?
- Once the page has loaded, yes. Since there's no server involved, cutting your internet won't stop them from working.
- Can I share formatted output with a colleague?
- We don't store anything, so there's no shareable link. Copy the output and paste it wherever: a PR comment, Slack, Notion, anywhere you need it.