SumizAI vs Lockbook

What Lockbook is

AlternativeTo files Lockbook under Note-taking. It is recorded as Freemium, Open Source — Unlicense, from United States. It ships on Mac, Windows, Linux, Android, iPhone, Android Tablet, iPad, Flathub and 2 more. The topics its entry raises are encryption, sync, self-hosting, handwriting and code.

That is our reading of the record. For AlternativeTo's own wording, see its page for Lockbook — the facts above were read on 2026-08-16.

What SumizAI is

A note-taking application built around a conversation with an AI model. You ask a question, the answer streams back, and the answers worth keeping become Markdown notes — filed into a vault that is a folder on your own disk.

A vault is a directory holding base.md, a generated table of contents up to six levels deep, and a notes/ folder with one .md file per note. Before a note is written it is checked against the ones already there, so the fourth note about the same idea gets merged instead of added. Links between notes are ordinary Markdown links to files that exist.

The model is never ours: you bring your own API key to one of seven providers — Anthropic, OpenAI, Gemini, Groq, OpenRouter, a local Ollama or your own server — and pay that provider directly. A question sends the table of contents plus at most five relevant notes within a 24,000-character budget, and the app shows you which five it used.

Side by side

Where they differ

• AlternativeTo's description of Lockbook does not mention an AI model. That is the whole starting point in SumizAI: you have a conversation with a model on your own API key, and the answers worth keeping become notes without you filing them.
• Lockbook is open source (Unlicense), and SumizAI is not. If reading the source is what decides it for you, that is a real argument for Lockbook. The guarantee SumizAI offers instead is structural rather than legal: the notes are Markdown files in a folder you chose, so they open in any editor whether or not the application is running.
• Lockbook is freemium: there is a free tier and a paid one, and the line between them is the thing to read before committing. SumizAI has one plan at a dollar a month, so there is no feature held back for a higher tier — and an unpaid account still opens and exports every vault it already has.
• AlternativeTo's description of Lockbook does not mention Markdown, so check what format your notes end up in before you fill it up. SumizAI writes standard .md files to a folder you picked, and an unpaid account can still export all of them.
• Lockbook advertises encryption. SumizAI answers the same worry a different way: on the desktop the notes never leave your disk, and the material a question sends to the model is capped at the table of contents plus at most five notes — and the app shows you which five it used.
• Lockbook can be self-hosted. SumizAI has nothing to host on the desktop — the vault is a folder on your machine — and if you want the model on your own hardware too, a local Ollama is one of the seven providers it speaks to.
• Lockbook supports handwriting or drawing. SumizAI is typed text only.

Which one to pick