The best open source alternative to Zen is Memos. If that doesn't suit you, we've compiled a ranked list of other open source Zen alternatives to help you find a suitable replacement. Other interesting open source alternatives to Zen are: Joplin, SiYuan, Notesnook, and AnyType.
Zen alternatives are mainly Note-Taking Tools but may also be Personal Knowledge Management (PKM) Tools or Secure & Encrypted Notes. Browse these if you want a narrower list of alternatives or looking for a specific functionality of Zen.
Memos is a self-hosted, open-source note-taking app built around a private timeline. Write in Markdown, skip the folder setup, and keep your data on your own server.

Memos is built around a single idea: capture the thought now, sort it out later. It presents notes as a private timeline rather than a hierarchy of folders, notebooks, or workspaces. You open it, write in Markdown, and move on. No title required, no template to fill out, no folder decision standing between you and saving something.
The timeline format makes it feel closer to a personal feed than a traditional note app. Each memo can carry tags, inline tasks, and links. Tags accumulate naturally as you write, and search works across everything when you need to find something later. The interaction stays light on purpose.
Markdown is the native format throughout. Notes stay readable outside the app, portable to other tools, and easy to back up as plain files. There's no proprietary format holding your content in place — unlike heavier knowledge base tools that lock structure into their own schemas.
Self-hosting is the core premise. Memos runs on your own server, stores notes in your own database, and keeps the full data path under your control. It's lightweight enough to run on a Raspberry Pi or a small VPS. No seat pricing, no paid feature tiers, no account required with a third-party service.
The MIT license means the source is fully inspectable and modifiable. Development happens publicly on GitHub, shaped in part by contributors who run Memos themselves.
Memos fits people who want a private place for operational notes, daily logs, saved links, and fleeting thoughts that don't belong in a project management tool or a shared chat thread. If you want something with end-to-end encryption baked in, Notesnook or Standard Notes are worth a look. If you want outlining and backlinks, Logseq goes much deeper. Memos doesn't try to be any of those things. It's a small, fast place to put things before they disappear.
Looking for open source alternatives to other popular services? Check out other posts in the alternatives series and openalternative.co, a directory of open source software with filters for tags and alternatives for easy browsing and discovery.
Cross-platform note-taking app with end-to-end encryption, Markdown support, web clipping, and sync via Dropbox, OneDrive, or Joplin Cloud.

Joplin is a note-taking app built around two principles: your data stays yours, and it works everywhere. It runs on Windows, macOS, Linux, Android, and iOS, with a terminal app for those who prefer the command line. Notes are stored in an open format, so you're never locked in.
The headline feature is end-to-end encryption (E2EE). Unlike Evernote or OneNote, Joplin encrypts your notes before they leave your device, meaning no third party can read them, not even the sync provider. For anyone serious about keeping notes private, that's a meaningful distinction.
What you can do with it:
Joplin Cloud, the optional hosted sync service, is based in France and subject to EU privacy law. It's a paid add-on, but Joplin works fine with Dropbox or OneDrive if you'd rather not pay.
The plugin ecosystem is mature. There are community-built plugins for task management, kanban boards, note templates, and more, making it closer to a personal knowledge base than a simple notepad. If you've outgrown Google Keep or want something more private than Apple Notes, Joplin covers a lot of ground without requiring a subscription.
Personal knowledge management system with WYSIWYG block editing, bidirectional links, spaced repetition flashcards, a relational database, and end-to-end encrypted sync.

SiYuan is a personal knowledge management tool built around a single core idea: everything is a block. Documents, headings, paragraphs, lists, even pages themselves are all blocks you can reference, link, move, and reorganize without breaking existing connections. It's aimed at people who want a Logseq- or Obsidian-style networked knowledge system but with stronger privacy guarantees and a fully offline-capable architecture.
The editing experience is WYSIWYG with Markdown support. SiYuan ships with 20+ block-level element types and 10+ inline elements, covering most typesetting needs out of the box. Widget blocks handle more specialized cases. Large documents with millions of words load smoothly through dynamic rendering, so file size doesn't become a bottleneck.
Key capabilities:
On the privacy side, all data lives on your device by default. Sync uses end-to-end encryption with incremental transfers to minimize bandwidth. No network connection is required to use it. SiYuan can also run as a local server accessible from a phone over a LAN, or be self-hosted via Docker for small-team collaboration with access controlled by an authorization code. For people comparing AppFlowy or AnyType, SiYuan's block-reference model and built-in spaced repetition are distinctive features that the others don't combine in one package.
End-to-end encrypted note-taking app with zero-knowledge architecture, cross-device sync, web clipper, and a self-hostable sync server.

Notesnook is a secure, encrypted note-taking app built around one principle: your notes are yours alone. Every note is encrypted on your device before it syncs anywhere. The company can't read your data. Neither can anyone else.
It's a direct alternative to Evernote, OneNote, and similar apps that store your notes in plaintext on their servers. Notesnook takes a different approach with XChaCha20 encryption and Argon2 key derivation, and you can verify it yourself using their open source tool, Vericrypt, which works entirely offline against real account data.
The full client and sync server are open source. You can self-host the sync server if you want complete independence from their infrastructure.
Key features:
Notesnook works well as a privacy-focused alternative to Joplin or Standard Notes for users who want a polished interface alongside strong encryption. The free tier covers the core experience across all platforms, with a paid plan for power users.
A local-first, encrypted workspace for notes, tasks, databases, and chats. Your data stays on your device, syncs peer-to-peer, and never passes through a central server.

Anytype is a local-first workspace where your data lives on your device, encrypted with keys only you hold. It's built for people who want the flexibility of a tool like Notion or Nuclino without handing their data to a company's servers. Notes, tasks, databases, wikis, and chats all live in one place, and none of it is readable by anyone but you.
The privacy model is the core differentiator. Anytype uses on-device encryption by default. No server sits between your devices; sync happens peer-to-peer over local networks. You can also self-host your own backup node. There's no account recovery through a third party because no third party ever has your keys.
Beyond privacy, it's a capable creation tool:
The object model is flexible. Everything in Anytype is an "object" with its own type and relations, which means a task, a contact, a note, and a project can all link to each other in structured ways. It's closer to a personal knowledge graph than a simple note-taking app.
For teams, Anytype supports shared spaces with collaborative editing, making it a self-sovereign alternative to tools like Affine for groups that need both privacy and real-time collaboration. A business tier adds features for larger organizations.
The underlying protocols are open, built by Any, a Swiss non-profit association, so third-party developers can build on top of them without permission.
Cross-platform note-taking app with end-to-end encryption, offline access, and powerful organization features for privacy-conscious users.

Standard Notes is a powerful, open-source note-taking application designed for those who value privacy and security in their digital lives. With a focus on simplicity and robust encryption, it offers a seamless experience across all your devices.
Key benefits of Standard Notes include:
Standard Notes offers both free and paid plans, allowing users to choose the level of features that best suits their needs. Whether you're jotting down quick thoughts, managing complex projects, or safeguarding sensitive information, Standard Notes provides a secure and versatile solution for all your note-taking requirements.
Looking for open source alternatives to other popular services? Check out other posts in the alternatives series and openalternative.co, a directory of open source software with filters for tags and alternatives for easy browsing and discovery.
A privacy-focused, offline-first note-taking app that stores everything on your device, with Markdown, note linking, file attachments, LaTeX math, and bring-your-own sync.

Beaver Notes is a local-first note-taking app that keeps your data on your device by default. There are no accounts to create, no servers to trust, and no telemetry phoning home. It's MIT-licensed and built for people who want full ownership of their notes without trading away convenience.
The core idea is simple: everything works offline, and you decide whether and how to sync. Instead of locking you into a proprietary cloud, Beaver lets you bring your own cloud provider to move notes across devices on your terms.
The feature set covers more ground than a basic editor:
Sharing is built in too. You can send notes to other apps or people directly, and shared notes carry their embedded drawings and files along with them.
Beaver sits in a different lane from cloud-dependent tools like Notesnook or Memos. It's not trying to be a team collaboration platform or an AI-assisted workspace. The focus is on a fast, distraction-free writing environment that respects your privacy by design, not as a setting you have to hunt down.
A customizable, offline-first note editor that lets you format text, create lists, add images, and export to HTML - all while maintaining your privacy.

Darkwrite is a feature-rich note-taking application designed for users who value both functionality and privacy. The editor supports essential formatting options like lists, text styling, and image embedding while maintaining a clean, distraction-free interface.
Key benefits:
Whether you're taking quick notes or working on longer documents, Darkwrite provides the perfect balance of features and simplicity while keeping your data private and secure.
OpenNotas is a multi-platform, end-to-end encrypted note-taking app that offers simplicity, synchronization, and offline functionality.

OpenNotas is a versatile and user-friendly note-taking application designed for personal use across multiple platforms. Here are its key features and benefits:
Simplicity: OpenNotas boasts an intuitive interface, allowing users to start writing notes immediately without navigating complex settings.
Multi-platform support: Available on various devices and operating systems, including mobile phones, computers, Windows, Linux, and macOS.
Synchronization: Users can sync their notes across devices through Adapter configuration, ensuring access to their information from anywhere.
End-to-End Encryption (E2EE): Utilizes AES algorithm to encrypt note data before storing it on the server, guaranteeing data security and privacy.
Offline functionality: OpenNotas can be used without an internet connection, with data stored locally and synced when connectivity is restored.
Free and open-source: The application is completely free to use and has its source code openly available.
Customizable sync options: Users can set up note syncing across devices through Adapter configuration, providing flexibility in how data is managed.
Data control: OpenNotas does not store user note data on its servers, giving users full control over their information.
Multiple language support: The application is available in various languages, including English, Vietnamese, and Traditional Chinese.
OpenNotas strikes a balance between simplicity and functionality, making it an excellent choice for users who prioritize privacy, ease of use, and cross-platform availability in their note-taking solution.
Justnote is a secure note-taking app that lets you easily create and sync notes across devices while maintaining full control of your data.

Justnote is a privacy-focused note-taking app designed for simplicity, speed, and data ownership. Key features include:
Justnote uses blockchain technology from Stacks to create a truly decentralized app where only you can access and control your account and notes. Your data is encrypted and stored on servers of your choice.
With Justnote, you can quickly jot down ideas, to-do lists, and other notes without worrying about privacy or losing access to your data. The clean, distraction-free interface lets you focus on your thoughts.
Whether you need a simple notepad for quick memos or a secure place to store sensitive information, Justnote provides an easy-to-use and private note-taking experience across all your devices.