Journli

I built a journaling app with E2E encryption and AI pattern analysis in 14 days — here's what I learned

I've been wanting to build a journaling app for a while. Not another Notion clone or mood tracker — something that actually reads what you write and says something true back.

The problem: I didn't want my private thoughts feeding someone else's model. So I made a decision early on — end-to-end encryption, client-side only. The AI sees your entries during analysis, in RAM, never stores them.

What I built in 11 days:

• SvelteKit + Supabase + @noble/hashes for crypto

• XChaCha20-Poly1305 encryption, DEK never leaves the browser

• 12-word BIP39 recovery phrase

• Gemini embeddings + RAG for pattern analysis

• Crisis detection

• Voice dictation via Gemini Audio

• Stripe subscriptions ($7/mo, $69/yr, 7-day trial)

• PWA installable on iOS and macOS

The AI part is where it gets interesting.

After ~2 weeks of my own entries I got this insight:

"There is something consistent in how you move through discomfort — work feels like something to rationalize rather than resist, the family situation gets named and then bracketed. You have a reliable way of processing difficulty: acknowledge it, accept it, move through it. What's quieter is whether there's room to let something just be hard."

That was grounded in specific entries, specific words I wrote. Not generic. That's when I knew this was worth building.

What surprised me:

The prompt engineering matters more than the model. Same Gemini, wildly different quality depending on whether you give it concrete examples of bad vs good output. "Ground every observation in specific moments" alone wasn't enough — I needed to show it what that means.

Where I am now:

14 entries indexed, character hypothesis building, entry-level chat launching soon. One paying user (my wife). Looking for the first external tester willing to write honestly for 2 weeks and tell me what they think.

Stack: SvelteKit · Supabase · Gemini · Stripe · Vercel · @noble/ciphers

Try it: journli.app