Cairn: Your Second Brain

Cairn is your second brain for every random thought.

The idea in the shower. A hidden spot you found on a trip. A friend's birthday. The thing you promised to do. Dump it into Cairn in a second and let your head go quiet. Cairn keeps it, understands it, and brings it back when it matters.

Use it however your brain works: ideas, places, reminders, to-dos, things to remember. No folders, no formatting, no rules.

DUMP IT
• Capture in a second from the home screen widget, a Quick Settings tile, or by sharing text from any app
• Voice notes are turned into text on your phone, so what you said becomes searchable
• Photos too: Cairn reads the words in a photo, so a picture of a whiteboard or a receipt turns up in search
• Pin a place to a thought, star the ones that matter, and set a reminder that rings on the minute

FIND IT IN PLAIN WORDS
• Ask the way you'd ask a friend: "all my ideas", "things to do", "what did I write in March"
• Search understands meaning, not just matching words. It knows an idea from a to-do and understands dates
• Find photos by what's in them
• See everything on a calendar, or browse by type, place or starred

CAIRN REMEMBERS
• Today shows one thing worth remembering: a thought from this day last month or last year, or something you meant to do
• Switch between a simple list and the Sky, where every thought is a star and related thoughts connect
• Build a cairn: a stone for every day you dump a thought, and rarer stones as it grows
• Miss a day and your cairn still stands

CAIRN+ — REMEMBERS YOU BACK
Try everything free first, no card needed. After that, Cairn+ is one payment, with no subscription.
• Echoes: write something you've thought before, and Cairn shows you the earlier thought, even months later
• Open loops: the things you said you'd do come back and ask whether you did them, before they go quiet
• Insights: your thinking style, your busiest hours and what's been on your mind
• Your own filters, like a morning to-do or an ideas list, filled as you capture
• Your cairn and streak as home screen widgets, with a capture button
• Extra accent themes, backgrounds and card styles

PRIVATE BY DESIGN
• Search and AI run on your phone. Your thoughts are never sent anywhere for AI
• No sign-up needed and no ads
• Lock Cairn with your fingerprint, face or screen lock
• Back up to your own Google Drive if you want to. It's off until you turn it on
• Export everything whenever you like. Free, always

Free forever: capture, search, the Sky, On this day, reminders, backup, export and app lock. There's no limit on how many thoughts you keep.

Cairn is made by one indie developer who kept losing his best ideas. Questions or ideas? Use the email below. Every message gets read.