Best open-source alternatives to Microsoft OneNote

Memos is an open-source, self-hosted note-taking application designed for quick capture and lightweight personal knowledge management. It is aimed at users who want a simple, timeline-first interface for creating Markdown notes without the overhead of folders or complex organization. The project emphasizes portability and self-hosting: notes are stored in Markdown, the app can be deployed with a single Go binary or via Docker, and it supports SQLite, MySQL, and PostgreSQL. It also presents itself as extensible through documented REST and gRPC APIs, making it suitable for integrations and custom workflows.

SiYuan is a personal knowledge management system designed around privacy and local control. It targets individuals who want to organize notes and knowledge using block-based editing, fine-grained references, and a Markdown-based WYSIWYG workflow rather than a traditional document-only model. The project emphasizes a broad feature set that includes large-document editing, databases, flashcards, export options, snippets, OCR, and an API for extension and integration. It also has a wider ecosystem of companion apps and components for mobile, desktop, marketplace content, and data repositories, suggesting it is aimed at users who want a cross-platform knowledge workspace with both local and deployment-oriented options.

Logseq is an open-source knowledge management and collaboration platform aimed at people who want a privacy-focused way to organize notes, tasks, and related information. It supports common note formats such as Markdown and Org-mode, and it emphasizes user control, longevity, and extensibility through plugins and themes. The README presents Logseq as suitable for students, professionals, and anyone managing personal or team knowledge workflows. It is available as a desktop application, has a web version for testing the DB version, and includes mobile apps. The DB version adds graph-based data, a new sync approach called RTC for real-time collaboration, and automated or SQLite database backup guidance because the feature set is still in beta/alpha.

Trilium Notes is an open-source note-taking application designed for users who want to build and manage large personal knowledge bases. It organizes content in a deeply nested tree, supports cloning notes into multiple locations, and provides a rich editor for text, code, diagrams, and structured note attributes. The project is aimed at people who want a self-hostable, cross-platform notes system with synchronization, sharing, and automation features. It runs as a desktop app or through a server-backed web interface, and it includes mobile access, import/export options, scripting, encryption, and a REST API for integration.