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The knowledge base for ChatGPT & Claude

Give ChatGPT & Claude long-term memory.

A simple knowledge base your AI can actually read. Save notes once. Stop re-explaining yourself.

Give your AI a memory See the loop

Free to start. No credit card required.

See a few example prompts by audience

Claude
Why did we switch from REST to gRPC for the internal APIs?
hjarni: get_note
✓
Your notes from the tech review: latency on the order service was 3x worse with JSON serialization. The team benchmarked protobuf and it cut p99 from 120ms to 40ms.
Claude
What did the Series A investors say about our margins?
hjarni: search_notes
✓
From the Sequoia meeting: they wanted gross margins above 70% before raising. You're at 64%.
Claude
What protocol did the Chen lab use for their cell viability assay?
hjarni: search_notes
✓
From your literature notes: Chen et al. used a flow cytometry protocol with 48-hour incubation. 92% viability at the target concentration.
Claude
What was the name of the fisherman I interviewed in Galveston?
hjarni: search_notes
✓
Your interview notes from March 12: Ray Guidry, 34 years shrimping the Gulf. He said the catch is half what it was in the '90s.
Claude
What was that ramen place near Fushimi Inari?
hjarni: search_notes
✓
Found it. Ramen Musubi on Fukakusa street. You rated it 9/10 for the tonkotsu broth.
See how developers use Hjarni

The problem

Sound familiar?

Claude starts every session from zero

You debugged that race condition last Tuesday. Wrote down the fix. Claude doesn't know. You re-explain the architecture. Again.

Your knowledge is scattered

Architecture decisions in Notion. Post-mortems in Google Docs. That one Slack thread with the deployment fix. Your AI can't see any of it.

Your tools do too much

Notion has 47 features you don't use. Obsidian needs plugins for everything. You just want to write something down and have your AI remember it.

More on this on the blog.

From a founder

Hjarni ran the whole Labeur launch. Scope decisions, landing page copy, App Store submission, launch day checklist, all in one place and all in sync with Claude. I stopped re-explaining myself to the AI. From first sketch to live in the store.
Joren De Groof, Not A Tech Company

Features

Simple on purpose.

Less software. More thinking.

Built for ChatGPT and Claude

Full REST API and native MCP server. Your AI reads and writes your notes directly. Set up ChatGPT or Claude in minutes.

Also for Cursor, Claude Code, Windsurf, and Cline.

Markdown, end to end

Notes are plain Markdown — the format your AI already speaks. No conversion. No lock-in.

Dump ideas fast

The inbox catches everything. Sort later. Don't let organizing slow down thinking.

Connect your thinking

Wiki-links between notes. Build a web of knowledge, not a pile.

Share a folder publicly

Turn any folder into a read-only public page. No sign-up for whoever you send the link to. See how.

Your data is yours

Export everything as Markdown in a ZIP. Always.

Automate with Zapier

Connect Hjarni to 9,000+ apps. No code. Notes arrive automatically, and your AI can use them right away. Set up Zapier

The loop

Every new chat starts from zero. Yours doesn't have to.

Debug in Claude. Save to Hjarni. Ship the fix. Repeat.

Start the loop

Teams

One person writes it down. Everyone's AI knows it.

Share a folder. Everyone's AI catches up instantly.

A shared Hjarni folder with notes written by four different teammates

Write once, the whole team remembers

A teammate documents the deployment fix. Now everyone's AI knows it. No more "did you see that doc?"

Set rules once, the whole team follows

New hires don't start from zero. Their AI already knows your stack and conventions. No more week-one ramp.

Share with your team How teams work

Simple pricing

No trials. No hidden fees. Start free and stay free as long as you want.

€ EUR £ GBP $ USD
Monthly Annual

Free

£0

forever

  • Up to 25 notes
  • Folders, tags & search
  • Full MCP & API access
Get started for free
Most popular

Pro

£8/mo

Billed monthly

  • Unlimited notes
  • File attachments
  • Share folders with 2 collaborators
  • Share folders publicly
  • Everything in Free
Go Pro

Teams

£10/seat/mo

Billed monthly

  • Shared knowledge base
  • Team MCP & API access
  • Member management
  • Billed separately from personal
  • Everything in Pro
Start your team

Common questions

Is this just another note-taking app?

No. It's a knowledge base your AI can actually use. Your notes become live context for every AI conversation.

Why not Notion or Obsidian?

Great tools. Different goals. Hjarni is built from the ground up for AI. Custom instructions per folder. Team-wide AI conventions. An MCP server designed around your knowledge — not bolted onto a workspace. See how Hjarni compares to Notion, Obsidian, ChatGPT Projects, Claude Projects, and Apple Notes.

What's MCP?

Model Context Protocol. An open standard that lets AI assistants connect to external tools and data. Hjarni has a built-in MCP server. Your AI reads and writes your notes directly.

Which AI assistants work with Hjarni?

ChatGPT and Claude connect via MCP today. Any AI that supports MCP will work automatically. Others can use the REST API.

How do I give my AI a memory?

Add Hjarni as an MCP server in ChatGPT or Claude. Takes two minutes. Every conversation picks up where the last one left off.

What happens to my data?

Your notes live on our servers. Export everything as Markdown anytime. We don't train AI on your data. We don't sell it. It's yours.

Can I collaborate with others?

Yes. Create a team, invite members, share folders. Everyone's AI benefits from the shared knowledge.

Can I self-host Hjarni?

Not currently. It's a hosted service. That keeps things simple — for you and for us.

Write once. You both remember.

Free to start. No credit card required.

Give your AI a memory

Works with Claude and ChatGPT today. Gemini coming soon.