Free Online Developer Tools — JSON, QR Codes, Passwords & More

JSON Formatter

Beautify messy JSON with syntax highlighting. Validate JSON structure, minify for production, and spot errors instantly with line numbers.

HTML Beautifier

Beautify minified or messy HTML code with proper indentation. Also minify HTML for production deployment.

Password Generator

Generate cryptographically secure passwords with custom length (8–128 chars), uppercase, lowercase, numbers, and symbols. Includes strength indicator.

QR Code Generator

Generate QR codes for URLs, text, contact info, WiFi, or anything. Customize size and colors. Download as PNG or SVG.

Random Number Generator

Generate single or multiple random numbers between any min and max value. Options for unique numbers, sorting, and copying results.

Regex Tester

Build and test regular expressions in real time. See matches highlighted instantly, inspect capture groups, and debug your patterns — all in your browser, nothing uploaded.

Diff Checker

Paste two pieces of text and instantly see line-by-line differences highlighted — additions in green, removals in red. Powered by an LCS diff algorithm, runs entirely in your browser.

UUID & Hash Generator

Generate cryptographically secure UUID v4 identifiers in bulk, and compute MD5, SHA-1, SHA-256, SHA-384, and SHA-512 hashes of any text — all processed locally in your browser.

Markdown to HTML Converter

Write or paste Markdown and instantly see a live HTML preview plus the generated HTML code — supports headings, bold/italic, links, images, lists, quotes, and code blocks.

Base64 Encoder/Decoder

Convert plain text to Base64 encoding or decode Base64 strings back to readable text — fast, accurate, and processed entirely in your browser.

JWT Decoder

Paste a JWT and instantly view its decoded header, payload, and signature in readable JSON — useful for debugging authentication tokens. Nothing leaves your browser.

CSV to JSON Converter

Paste CSV data with a header row and instantly convert it into a clean, structured JSON array — handles quoted fields and commas correctly, runs in your browser.

Android App Icon Sizes 2026: The Complete Guide (mdpi to xxxhdpi)

A complete reference for Android app icon sizes across all density buckets, plus the Play Store icon — and a free tool to generate them all at once.

iOS App Icon Size Guide: Every Size Apple Requires for App Store (2026)

A complete reference for every iOS app icon size Apple requires, including the special rules for the 1024px App Store icon — plus a free generator.

How to Create a Complete PWA Icon Set (Favicon, Apple Touch, Manifest) for Free

A step-by-step guide to generating and wiring up a complete PWA icon set — favicons, Apple touch icon, and manifest icons — for free.

Free Favicon Generator: Create Every Favicon Size from One Image

A missing favicon makes a site look unfinished. Generate every favicon size you need from one image, free, with the code to wire it up.

Android Adaptive Icons Explained: Square, Rounded & Circle Masks

Android launchers can mask your icon into a circle, squircle, or rounded square. Here is how to design for it, with a free shape preview tool.

How to Create a QR Code for Anything — Free in 10 Seconds

QR codes are everywhere — restaurant menus, business cards, posters. Creating one for yourself is completely free and takes ten seconds. Here is how.