What is Obsidian? Markdown notes stored on your device, links like Wikipedia, and use with AI

What is Obsidian?

Obsidian is a note-taking application focused on data ownership, with the tagline on its homepage being "Sharpen your thinking". Three principles, according to Obsidian (checked on 23/10/2026) and the homepage (per Obsidian), are:

1. Your thoughts are your own: notes are stored privately on your device.
2. Your mind is unique: thousands of plugins and themes to customize.
3. Your knowledge should last: open file format, no lock-in.

Obsidian is free and unlimited, according to the pricing page, requires no signup, and the applications do not collect telemetry data nor sell user data. For example, a Mac user can create a vault in an iCloud folder and open it on iPhone using Obsidian. Also, because notes are Markdown files, you can still read them with any text editor if you ever leave Obsidian.

How does Obsidian store data?

Obsidian stores notes as plain text Markdown files, according to Obsidian (read on 23/10/2026) and documentation (per Obsidian), in a vault, which is a folder on your system's file system, including subfolders. Because they are plain text, you can use another editor to modify them and Obsidian will refresh when changes happen from outside. You can create a vault anywhere your operating system allows, and sync using Obsidian Sync, Dropbox, iCloud, OneDrive, Git and many other services.

A .obsidian folder at the vault root contains vault-specific settings like hotkeys, themes and community plugins. The documentation notes: do not create a vault inside another vault because internal links only have scope within one vault, and if using Git you may add workspace layout files to .gitignore.

Type	Supported format
Notes	Markdown .md
Database	Bases .base
Whiteboard	JSON Canvas .canvas
Images	avif, bmp, gif, jpeg, jpg, png, svg, webp
Audio	flac, m4a, mp3, ogg, wav, webm, 3gp
Video	mkv, mov, mp4, ogv, webm
Documents	pdf

What are Obsidian's main features?

• Links and backlinks: you connect notes with internal links, and a backlinks section shows which notes point to the current note.
• Graph view: displays relationships between notes as an interactive graph to see hidden patterns in your thinking.
• Canvas: infinite space for research, brainstorming, diagramming and laying out ideas; saves as open JSON Canvas files.
• Properties and Bases: Bases is a core plugin that creates "database-like views" of notes: view, edit, sort, filter by properties; display as table, list, cards, kanban or map. Data remains in Markdown files and their properties.
• Daily notes, templates and other core plugins: Daily notes, Templates, Search, Backlinks, Outline, Properties view and much more are in the core plugins group.
• Community plugins: the homepage lists examples like Calendar, Kanban, Dataview, Outliner, Tasks and says there are thousands of plugins and themes.
• Web Clipper and command line: there is a tool to clip web pages into notes, and Obsidian CLI lets you control the app from terminal for scripting (requires version 1.12.7 or higher and the app must be running).

How Much Does Obsidian Cost?

Obsidian is free; only optional add-on services are paid. According to the official pricing page (checked 23/10/2026), prices in USD are:

Item	Price	Notes
Obsidian app	Free	Unlimited, no registration required
Sync	$4 per user per month (annual billing), $5 (monthly billing)	Sync multiple devices, end-to-end encryption, version history (one year), collaborate on shared vault
Publish	$8 per page per month (annual billing), $10 (monthly billing)	Publish notes to web, customizable interface, full-text search
Catalyst	$25 one-time	Support development, early beta access, community badge
Commercial license	$50 per user per year	Not required

Do I need to buy a commercial license and can I get a refund?

The commercial license is $50 per user per year, according to Obsidian, and the pricing page makes clear you are not required to buy it. Additionally, if you use Obsidian for work within an organization, Obsidian encourages purchasing to keep the project independent and fully user-funded. Sync and Publish are fully refundable within 7 days; Catalyst, commercial license, and Obsidian Credit are not refundable. Students, teachers, and nonprofit organization staff get 40% off Sync and Publish. For example, a group of 3 users on annual Sync billing pay $4 per user per month. With Sync, data is encrypted end-to-end with AES-256 so Obsidian cannot read it.

Are community plugins safe?

Community plugins run with the full permissions of the application, so only enable them if you trust the author. According to official documentation, Obsidian runs by default in Restricted Mode to block third-party code; you disable it only when you trust the plugin author. Due to technical constraints, Obsidian cannot limit plugins by specific permissions: plugins can access files on your machine, connect to the internet, and install additional programs. All plugins must comply with the developer policy; each version is automatically scanned for vulnerabilities, code quality issues, and malware, with results displayed as a safety score on the plugin page, and popular, featured, or reported plugins are also manually reviewed. If you work with sensitive data, the documentation recommends you independently audit plugins before using them.

Does syncing replace backup?

Syncing does not replace backup, because those are two different things. This distinction is emphasized, according to Obsidian (read 23/10/2026) and backup documentation (per Obsidian):

1. Syncing (Sync, iCloud, OneDrive, Dropbox) keeps files the same across all devices, so a deleted or corrupted file spreads everywhere.
2. Backup is a copy elsewhere to restore if needed.

For example, if you accidentally delete a folder in your vault on Mac, iCloud will delete that folder on iPhone, while a one-way backup still keeps the old version. So use a separate backup tool to create one-way copies, and if you use multiple devices, pick one main device as the backup location. Also, the File recovery plugin is useful but limited and saves per device. OPCAIOS syncs the vault through iCloud and still considers that not a backup.

How is Obsidian different from Notion?

Obsidian differs from Notion in where data is stored. Obsidian stores Markdown files on your machine and you choose how to sync, while Notion is a cloud workspace with a database and browser collaboration. The two tools suit two different use cases:

1. Obsidian suits you if you value file ownership, work offline, and want other tools (including AI) to read your directory directly.
2. Notion suits you if you need multi-person team collaboration and beautiful data tables.

For example, an individual taking research notes and using an AI agent to read notes on their machine suits Obsidian. A sales team needing a shared customer table in the browser suits Notion. The free app and Sync service, according to Obsidian's pricing page (checked 23/10/2026), with collaboration on shared vault starting at $4 per user per month (per Obsidian). See details about Notion in the post What is Notion?.

How to use Obsidian together with an AI agent?

Because notes are Markdown files in a directory, AI agents like Claude Code can read and write directly without needing special integration. That's why many people use Obsidian as long-term memory for AI. According to Obsidian documentation (checked 23/10/2026), Obsidian CLI also allows controlling the application by command, for example opening daily notes, adding tasks, searching in a vault. A few points to keep in mind:

1. Don't put secrets in the vault: API keys, passwords, .env files. Vaults are usually synced through other services so secrets can easily leak out.
2. Have one-way backup before letting an agent make bulk changes; review the changes (diff) if the vault uses Git. See What is GitHub?.
3. Grant minimum permissions and only enable plugins you trust; see the principles in What is MCP?.
4. Have a root instruction file (for example AGENTS.md) so the agent knows the structure and rules of the vault, similar to providing reference documentation to AI in AI writes code in wrong version.

OPCAIOS's experience using Obsidian as shared memory

OPCAIOS uses one Obsidian vault as a place to store knowledge, processes and work logs, synced through iCloud, for both people and AI agents to read together. The structure includes a root instruction file telling the agent what to read first, a system status file, daily logs and tool notes written in Markdown with a YAML header (title, tags, status, links) and links in the form [[...]]. A few rules we set: new tool notes or instructions after research are all saved to the vault; we don't put binary files, cache, credentials or .env files in the vault because the vault is on a sync service; and after each work session we update the status file and log so the next session (including AI) knows what work is in progress. We still consider iCloud sync not to be a backup, exactly as Obsidian's documentation emphasizes.

How to get started with Obsidian?

1. Download the app from obsidian.md (available for Windows, macOS, Linux, mobile).
2. Create a vault in a directory you control.
3. Create your first note and write in Markdown.
4. Link notes using [[note name]] and see backlinks.
5. Turn on a few core plugins like daily notes and templates; only add community plugins when you have a clear need.
6. Set up separate backups before storing a lot of data.

Read more: How to turn Obsidian into a smart virtual assistant.

Frequently asked questions

What is Obsidian?

It's a free note-taking app that stores plain-text Markdown files in a directory on your computer, allowing you to link notes, view relationship graphs, draw Canvas and customize with plugins.

Is Obsidian free?

Yes. The app is free with no limits and doesn't require registration, including for work use. Only Sync (from 4 USD per month) and Publish (from 8 USD per month per page) are optional paid services; a commercial license costs 50 USD per year and is not required.

Where is Obsidian data stored?

On your machine, in a directory called a vault, as Markdown files. You can sync through Obsidian Sync, iCloud, Dropbox, Git or other services, but syncing is not the same as backup.

Are community plugins dangerous?

Plugins run with the permissions of the app: they can read files, make network connections and install programs. Obsidian has a restricted mode by default and automatic scanning, but you should only enable plugins from authors you trust and do additional review with sensitive data.

How to use Obsidian with AI safely?

Keep secrets outside the vault, have one-way backup, give the agent minimum permissions and review changes before accepting. Want to learn how to work with AI on a structured process, check out OPCAIOS's AI application training course.

Source: obsidian.md homepage and pricing page, checked 23/10/2026; official Obsidian help documentation (source code at obsidianmd/obsidian-help repository): "How Obsidian stores data", "Accepted file formats", "Plugin security", "Introduction to Bases", "Obsidian CLI", "Back up your Obsidian files". Prices and features may change. Vault usage experience is from OPCAIOS; we do not publish note contents.