Free Online Toolbox
Image & PDF converters, JSON formatter, Base64, word counter and more — handy online tools in one place. Everything runs locally in your browser: no files or data leave your device, no install, no sign-up, completely free.
- 🔒 Data never leaves
- ⚡ Instant results
- 📱 Works on mobile
- 🆓 Completely free
Image & PDF Converters
View all →All Tools
View all →JSON Formatter
Beautify, minify and validate JSON in one click, with automatic error detection.
Base64 Encode / Decode
Convert text to and from Base64, with full UTF-8 and URL-safe support.
Word Counter
Instantly count words, characters, sentences, paragraphs and reading time.
Case Converter
Switch between UPPERCASE, lowercase, Title Case, camelCase, snake_case and more in one click.
Hash Generator
Generate MD5 / SHA-1 / SHA-256 / SHA-384 / SHA-512 hashes at once.
Password Generator
Generate strong random passwords with custom length and character sets, using cryptographic randomness.
QR Code Generator
Turn a URL or text into a QR code instantly and download it as PNG — free.
JSON ⇄ YAML Converter
Convert data between JSON and YAML in your browser — free, fast and no upload.
From the blog
All articles →AVIF vs WebP vs JPEG: Which Image Format Wins?
A practical head-to-head of AVIF, WebP and JPEG — compression, quality, transparency and support — so you know which to use for photos and for the web.
Base64 vs URL Encoding: What's the Difference?
Base64 and URL (percent) encoding both turn data into safe text — but for different reasons. Here's what each does, when to use it, and how they combine.
The Best Image Format for Websites in 2026
Which image format should you use on a website? A quick, practical guide to picking WebP, AVIF, JPG, PNG or SVG for speed, quality and compatibility.
Why choose Yunknow Toolbox?
🔒 Privacy first
Every operation runs on your device with JavaScript. Whatever you paste is never sent to a server or stored — safe for passwords, keys and sensitive text.
⚡ Blazing fast
Static pages on a global CDN load instantly, and every tool responds in real time without any round trips.
🧭 Simple to use
A clean interface with no clutter. Each tool comes with clear instructions and an FAQ, so beginners can start right away.
📱 Cross-device
Responsive design that works great on desktop, tablet and phone, with both light and dark mode.
All 38 of our converters have been run against the same test images, with every output byte measured — no estimates anywhere. Sometimes the result contradicts intuition: a UI screenshot converted from PNG to JPG went 18.0 KB → 43.5 KB, up +142%, while the same photo from PNG to WebP went 1.88 MB → 303.1 KB (-84%). Both numbers are published in the Conversion Lab, with the source files so you can re-run them yourself.