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Name: Kosshi
Price: 24.99 USD
Author: Junichi Sato

Materials for writing about Kosshi. The text and images on this page may be used in articles, reviews, and videos.

About

Kosshi is a fast, native outliner for Mac, iPhone, and iPad.

Kosshi is an outliner built for responsiveness above all. It is a native app built with Apple frameworks, designed so that typing and moving rows stay fast even in outlines beyond 100,000 rows. Markdown renders as you type, and images and PDFs sit inside the outline. Data is stored on your devices and in your own iCloud account, and no Kosshi account is needed. After a 7-day free trial, one purchase covers Mac, iPhone, and iPad.

Highlights

Speed: A native app with its own rendering engine. Display, scrolling, editing, and search are tested on outlines of 100,000 rows.
Markdown and images: Formatting renders in place, and images, PDFs, and videos preview inside rows. On iPad, sketches can be drawn with Apple Pencil.
Mac, iPhone, iPad, and iCloud: Sync uses CloudKit. The developer cannot see the contents of your data.
One-time purchase: No subscription.

Facts

Platforms: macOS 14 or later, iOS and iPadOS 17 or later
Price: 7-day free trial, then a one-time purchase of US$24.99. Prices vary by region. One purchase covers Mac, iPhone, and iPad.
Developer: Junichi Sato, Japan
App Store: apps.apple.com
Website: kosshi.app
Forum: forum.kosshi.app

About the developer

I'm Junichi Sato, a software engineer in Japan. I started building Kosshi in early 2022 and shipped it in 2026. The icon and illustrations are drawn by my wife, the illustrator NAOYOSHI.

Why I built Kosshi →

Blog: shirokumamake.com