Notion and Obsidian both get sold as a second brain, but they are built on opposite ideas. Notion is a cloud workspace where your notes live on Notion's servers. Obsidian is an app that reads and writes plain Markdown files in a folder on your own computer. Almost every difference follows from that.
Start with price. Obsidian itself is free, and since February 2025 that includes use at work. The commercial license that companies used to need is now optional. You pay only for add-ons: Sync is listed at $4 a month billed yearly or $5 monthly, and Publish, which turns notes into a website, at $8 a month per site billed yearly or $10 monthly. Notion has a free plan for individuals, and its Plus plan is $10 per seat a month billed yearly or $12 monthly.
Data ownership is where Obsidian wins clearly. Your notes are ordinary text files. You can open them in any editor, back them up however you like, and keep them in a folder that will still read fine in twenty years. If Obsidian disappeared tomorrow, you would lose an app, not your notes. Notion can export to Markdown, CSV and HTML, but databases, relations and layouts do not survive the trip intact.
Collaboration is where Notion wins clearly. Shared pages, comments, permissions and real-time editing are built in. Obsidian is designed for one person. Sharing a vault with a team is possible, but it is not what the app is for.
Structure is the other big split. Notion's databases let you build trackers, content calendars and CRMs with views and filters, with no code. Obsidian's strength is linking. Notes connect through backlinks and a graph view, and a large plugin ecosystem adds almost anything else, including database-style views, if you are willing to set it up.
Privacy follows the same line. Obsidian's local files never leave your machine unless you sync them. Everything in Notion lives in its cloud.
The short version: pick Obsidian if you work alone, care about owning your files, or want it free. Pick Notion if you share notes with a team or want databases without building them yourself. Plenty of people use both: Notion for shared work, Obsidian for their own thinking.
