Best Free & Open Source Alternatives to Microsoft OneNote

NoteDiscovery is an open-source, self-hosted knowledge base designed for personal note-taking and knowledge management. Built with a modern JavaScript stack and FastAPI backend, it provides a clean interface for capturing and organizing your thoughts.

The application supports markdown formatting, making it easy to write and format notes. It is designed around the Zettelkasten methodology, a powerful system for connecting ideas and building a personal knowledge network.

As a self-hosted solution, NoteDiscovery gives you complete control over your data and privacy. It can be easily deployed using Docker, making setup straightforward for users familiar with containerization. Whether you are looking to replace Notion, Evernote, or Obsidian with a privacy-focused alternative, NoteDiscovery offers a compelling option.

Scratch is a minimalist, offline-first markdown note-taking app built for macOS, Windows, and Linux. Unlike cloud-based alternatives, Scratch stores all your notes as plain .md files that you fully own — no account required, no internet connection needed.

It features WYSIWYG editing that saves as markdown, a preview mode for any .md file via drag-and-drop or "Open With", markdown source mode toggle, syntax highlighting for 20+ languages with a GitHub-inspired color scheme, Mermaid diagram support, KaTeX math rendering, wikilinks with autocomplete, slash commands for quick formatting, focus mode for distraction-free writing, and optional Git integration for version control and multi-device sync.

Scratch is built with Tauri, React, and Tailwind CSS, making it lightweight — 5-10x smaller than Obsidian or Notion. It also integrates with local AI tools like Claude Code, OpenAI Codex, OpenCode, or Ollama for editing notes with AI, and detects external file changes so it works seamlessly alongside other tools.

kuku is an open-source, local-first Markdown workspace for macOS designed for people who want their notes to stay portable, private, and useful to AI. It edits ordinary .md files in a local vault, then layers search, graph navigation, AI assistance, Second Brain workflows, and encrypted sync on top.

The app connects notes with [[wikilinks]], backlinks, and 2D/3D graph navigation, turning your vault into a personal wiki. AI features include Agent, Ask, and Inline editing modes with diff-based approval, so proposed changes are always reviewable before they are applied. Decision documents help AI context improve explicitly over time by turning proposals into traceable memory and wiki updates.

Built as a full-stack open-source project, kuku includes the macOS client, web app, Go server, protobuf contracts, Rust AI/indexing crates, and Docker infrastructure. You can use it entirely offline, sign in for managed convenience, or self-host the complete stack yourself.

Anchor is an offline-first, self-hostable note-taking application built around speed, privacy, and reliability across web and mobile. Notes are stored locally, fully editable without an internet connection, and synced across devices when you come back online, so your data is always available and always under your control.

The app ships with a rich text editor (bold, italic, underline, headings, lists, checkboxes), custom tags with colors, image and audio attachments, customizable note backgrounds, pinning, archiving, and a soft-delete trash with a recovery period. Notes can be shared with other users on the same instance as either viewers or editors, and an admin panel handles user management, registration control, and system statistics. Authentication is handled locally or via any OIDC provider such as Pocket ID, Authelia, Authentik, or Keycloak.

Unlike Google Keep, which is locked to Google's ecosystem and account system, Anchor runs as a single Docker container (with an optional external PostgreSQL database) that you host on your own infrastructure. There is no telemetry, no vendor lock-in, and your notes never leave your server unless you explicitly share them. It is a great fit for anyone who wants Keep's lightweight feel combined with the privacy, portability, and long-term control of self-hosted software.

HelixNotes is a local-first markdown note-taking application built with Tauri, SvelteKit, and Rust. Unlike cloud-based alternatives, it stores your notes as standard Markdown files on your local filesystem — giving you complete ownership and zero vendor lock-in.

The app features a rich WYSIWYG editor powered by TipTap with slash commands, tables, and code highlighting, alongside a source mode for raw Markdown editing. You can link notes with [[wiki-links]] and explore connections through an interactive graph view. Full-text search is powered by Tantivy for instant results across your entire vault.

HelixNotes supports KaTeX math rendering, Mermaid diagrams, daily notes with a built-in calendar, version history with diffs, automatic backups, and AI writing tools via local Ollama or your own API keys. It runs natively on Linux, Windows, macOS, and Android without Electron — making it significantly faster and lighter than many competitors.