Hello — I'm Junichi, and I made Kosshi.
A few years ago I was writing a technical book and noticed that sketching the structure first made the writing go much more smoothly. Around the same time I was juggling several personal projects, with information drifting apart across different tools, and I started to want an outliner of my own.
What I was after was something that worked the same way on Mac and iPhone, could place images alongside text, and kept its data on my own devices. I couldn't find it, so I made one. That's Kosshi.
It's a native Mac and iOS app, with a rendering engine written from scratch, designed to stay smooth even with large outlines. Sync is over iCloud — no account, no server I run; your data lives only on your devices and in your iCloud.
If you live in an outliner, I'd love to hear what you find.
feels like a very honest builder story, you needed a calm, private outliner that worked the same way across Mac and iPhone, so you made one.I like the no-account/no-server approach. Outlines often hold unfinished thinking, not just polished notes.what was harder to get right: performance with large image-heavy outlines, or keeping the experience simple across both Mac and iOS?
About Kosshi on Product Hunt
“Simple, fast outliner for Mac and iPhone.”
Kosshi launched on Product Hunt on May 23rd, 2026 and earned 88 upvotes and 5 comments, placing #10 on the daily leaderboard. Kosshi is a simple native outliner for macOS and iOS. Fast and focused outline editing.
Kosshi was featured in Mac (103.5k followers), Productivity (652.2k followers) and Writing (59.2k followers) on Product Hunt. Together, these topics include over 153.6k products, making this a competitive space to launch in.
Who hunted Kosshi?
Kosshi was hunted by Junichi Sato. A “hunter” on Product Hunt is the community member who submits a product to the platform — uploading the images, the link, and tagging the makers behind it. Hunters typically write the first comment explaining why a product is worth attention, and their followers are notified the moment they post. Around 79% of featured launches on Product Hunt are self-hunted by their makers, but a well-known hunter still acts as a signal of quality to the rest of the community. See the full all-time top hunters leaderboard to discover who is shaping the Product Hunt ecosystem.
Want to see how Kosshi stacked up against nearby launches in real time? Check out the live launch dashboard for upvote speed charts, proximity comparisons, and more analytics.
Junichi Sato