KatakataAspect ratio calculator
Find a missing width or height from any ratio. Handy for video, images, and responsive layouts.
Use tool →English tools
A small lab of
free browser tools.
KatakataLab.
Everyday utilities for design and writing—grown from real work. No account needed. Open a tool, use it in the browser, and go back when you need it again.
Tools you can use now
Each page includes the working tool. Most inputs stay in your browser—see the note on each tool.
px / rem converter
Convert pixels and rem both ways, adjust the root size, and copy CSS-friendly output.
Use tool →QR Maker Lab
Build QR codes for URLs, Wi-Fi, and more. Check readability, then save from the browser.
Use tool →Text diff checker
Compare two texts or code snippets side by side. Spot additions and deletions quickly.
Use tool →Japanese web font lab
Compare Japanese fonts with live text. Tune size, weight, and spacing, then copy CSS.
Use tool →Emphasis lines studio
Create manga-style focus and speed lines for thumbnails. Export PNG or SVG—no account.
Use tool →Social share preview
Preview title, description, and image for X, Facebook, and LINE-style cards before you post.
Use tool →Social image sizes
Working ratios for previews and thumbnails, plus a safe area when crops are unpredictable.
Read guide →Password security basics
Length, unique passwords, and managers—plain-language tips that still hold up today.
Read guide →A quick note
This English area is a lighter entry point into the same lab as the Japanese site. Tools are free browser utilities; the full guides and experiments live mainly in Japanese.
Don’t paste passwords, private customer data, or regulated records into any public web tool unless you trust the page and understand how it works.
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