About Us

Yunknow Toolbox is a free online toolbox for anyone who works with images, files, text and data — developers, designers, writers and everyday users alike. We believe good tools should be simple, fast and respectful of your privacy — no install, no sign-up, just open the page and use them.

What you'll find here

Yunknow Toolbox brings together dozens of tools across four areas: image & PDF converters (convert between JPG, PNG, WebP, AVIF, SVG and HEIC, and merge, split, compress, rotate or delete PDF pages), developer tools (JSON and XML formatting, Base64, JWT decoding, hashing, regex testing, cron expressions and more), text tools (case conversion, text diff, word counting, cleanup and Morse code) and generators (passwords, UUIDs, QR codes and Lorem Ipsum). Alongside the tools, our blog publishes in-depth guides that explain the concepts and common pitfalls behind them.

Who it's for

Developers who need a quick formatter without pasting code into an unknown server; designers converting and optimizing assets; students learning how encodings, number bases or hashing work; and anyone who just wants to resize an image or combine a few PDFs without installing anything. Every tool works on both phone and desktop, supports dark mode, and is available in 繁體中文, English, 日本語 and Deutsch.

Our philosophy

Many online tools send whatever you paste to a server, which is far from ideal when your content contains passwords, keys or sensitive data. That is why our tools run locally in your browser wherever possible: your input never leaves your device, and we neither store nor log it.

Technology and performance

The site is built with static site generation and a global CDN, so pages load instantly and stay lightweight, optimized for mobile and dark mode. We also offer multiple languages and keep an eye on Core Web Vitals.

How we check what we tell you

It is easy to write "WebP is smaller than PNG" and never back it up — pages on this site used to do exactly that. Not any more: every file size shown on all 38 of our converters was produced by opening our own pages, putting test files through them, and reading the exact byte length of the output. There is no estimation step anywhere in it. The four test images are drawn from scratch by a script with a fixed random seed, so every run produces identical results, and every source file is published for download — anyone can repeat the measurement and check our numbers. The method, the full results, and an honest list of what we did not measure and why, are all in the Conversion Lab.

Sometimes the answer contradicts the common wisdom, and we publish it anyway. Take a screenshot of an application from PNG to JPG and the file does not shrink — it grows by 142%. That number is useful to you, so it goes on the page even when it makes one of our own tools look less universal.

Who maintains this, and how

This site is run and maintained by Yunknow — questions and suggestions reach the same person who writes the tools. There is one design rule behind everything here: if it can be done in your own browser, it should not be sent to someone else’s server. That is why no tool on this site asks you to upload a file, and none asks you to create an account.

This is a small independent site, not a content farm. The content in all four languages is written for that language rather than translated from the English version — you can check this yourself: the examples and the pitfalls called out for the same tool differ across the four locales. It is also why we deliberately stay at four languages: four done properly beats twenty spread thin.

The maintenance is auditable. Before any change goes live, a site-wide script checks all 536 indexable pages for heading structure, canonical URLs, hreflang across four languages, structured data, broken internal links, orphaned pages, content duplication, image dimensions and accessible names on every form control. If a single check fails, the change does not ship. If you find a page that does not meet the standard described here, please tell us — that is a gap on our side.

Support us

Yunknow Toolbox is completely free. To keep it running and build new tools, the site shows a small amount of advertising, and we do our best to keep ads unobtrusive. If these tools help you, please share them with friends or colleagues.

Feedback

Want a new tool, found a bug, or have a suggestion? Tell us via the contact page — your feedback drives our improvements.