KnowledgeBrain is live: a local-first second brain, free for one week

Notes pile up until you stop opening them — so I built KnowledgeBrain.

It’s a local-first AI second brain: text, voice, PDFs, and ebooks in one library you can ask questions of, with citations back to the source. Data stays on your devices and in your iCloud. No account. No tracking.

Free for one week: download at no cost for about seven days from today, then it returns to paid.

Store note: for App Review compliance, it is not available on the China mainland App Store. Use a Hong Kong / US / Taiwan (or other non-mainland) Apple ID:

https://apps.apple.com/app/knowledgebrain/id6794209806

Why this exists

You’ve probably been here: a meeting scribble, a voice memo on the commute, three clipped articles, half a PDF highlighted — six months later you need “what did I say that day,” and you’re digging through folders, Notes, and chat history.

Search wants keywords. You remember meaning. Knowledge turns into clutter instead of usable memory.

KnowledgeBrain’s job is simple: turn your own materials into a library you can ask. Every answer cites sources you can open. Not another cloud chatbot — a second brain that only knows your stuff.

What it does

Capture widely: quick text, on-device voice transcription, PDF / EPUB / Markdown, photo OCR, share-sheet save.

Ask your library (RAG): answers with citations you can trace to the original passage.

On-device first: vector search, speech, and OCR run locally; Apple Intelligence devices can generate answers on-device too.

BYOK: your own API key (OpenAI / Anthropic-compatible, including DeepSeek, Zhipu, OpenRouter, and more) in the system Keychain.

Auto-organize: summaries and tags; semantic search by meaning, not just exact words.

Yours to sync and export: private iCloud sync across devices; one-tap Markdown export — never locked in.

Who it’s for

Developers and technical folks

You bring your own key and care where data lives. You want a tool you control, not another “hand over notes for features” subscription.

Researchers, writers, consultants

Lots of material, heavy on citations. You need “where did this sentence come from,” not an unverifiable AI mashup.

People who already do PKM

Markdown / Obsidian / PDF piles, and you want capture on the phone plus natural-language questions against your own library.

Privacy- and offline-minded users

No account, no ads, no tracking. Core search and capture stay local; cloud is optional and yours to turn on.

Less of a fit if you want “auto-remember everything with zero setup,” refuse any API config, or won’t use a non-mainland App Store — the bar will feel high. It’s a knife you hold, not a kitchen that cooks for you.

Why one free week

Just cleared review. I want people who need this tool to try it and send feedback. After the week it goes back to paid; early adopters keep capabilities as promised on the product page and release notes.

If your problem is “I wrote a lot and still can’t ask it” — this week might be worth a download.

Guide: https://32comic.github.io/knowledgebrain-site/guide.html?lang=en

Privacy: https://32comic.github.io/knowledgebrain-site/privacy.html?lang=en