Emphasis Lines Studio
Create focus, speed, manga, and radial emphasis lines in your browser, adjust their shape and color, then export PNG or SVG assets without an account.
Open tool →Choose a tool
Japanese Web Font Lab
Compare Japanese web fonts with editable text, tune size, weight, spacing, and line height, then copy practical CSS while learning how font loading affects performance.
Open tool →Aspect Ratio Calculator
Calculate a missing width or height from any aspect ratio, detect common ratios, swap orientation, and preview the result for video, images, CSS, and responsive layouts.
Open tool →PX to REM Converter
Convert pixels and rem units in both directions, change the root font size, preview readable text, and copy CSS variables, SCSS variables, or utility-class output.
Open tool →Browser Text Diff Checker
Compare two text or code versions in your browser, inspect additions and deletions by line or character, switch split and unified views, and copy the result.
Open tool →QR Forge Lab
Create QR codes for URLs, Wi-Fi, email, phone, social profiles, and contacts, check contrast and quiet zone quality, then save the result from your browser.
Open tool →Social Share Preview Simulator
Preview a title, description, site name, and image in X, Facebook, and LINE-style cards, check the image ratio, and catch likely cropping before publishing.
Open tool →Social image size guide
Use current working ratios for link previews and thumbnails, understand which values are platform guidance, and plan a central safe area for unpredictable crops.
Read guide →How the English section is maintained
English pages use separate, self-canonical URLs and link back to equivalent Japanese pages with reciprocal language annotations. They are written and reviewed as complete entry points rather than generated keyword variants. We do not redirect visitors by browser language, so a saved URL remains predictable.
New English pages are intentionally ad-free while their usefulness and search behavior are evaluated. Browser-side processing does not mean every page has zero network requests: fonts, analytics, or libraries may still be requested as described on the relevant page. Never paste credentials, private customer records, or regulated data into an unapproved web tool.
Last editorial review: . Created and maintained by Katakata. Corrections are welcome through the contact page.