Twain
Twain vs Obsidian
Obsidian is a free, local-first knowledge base with 5,800+ community plugins. Twain opens a single Markdown or MDX file from Finder, with no vault and nothing to set up.
Not shipped yet. The signed, notarised build is in progress; the download and checkout open together when it's ready.
The short version
These are different kinds of tool, and Obsidian is free, so be clear about what you actually need. Obsidian is a local-first personal knowledge base: plain Markdown in a folder, thousands of community plugins, graph view, backlinks, Canvas, and apps on every platform including iOS and Android. What it will not do today is open one file. It requires a vault, and adding someone else's docs folder as a vault writes an .obsidian directory into their repo. Obsidian lists opening individual Markdown files as planned on its public roadmap, and the request has been open since May 2020. Twain does that job right now, plus Quick Look, safe MDX rendering and block-based editing. Building a second brain is Obsidian's category. Reading a docs folder is less work in Twain.
you want to read, review or edit Markdown and MDX that already lives somewhere, a docs repo, a folder an agent wrote into, a download, without adopting a vault, and you want Finder Quick Look and real MDX rendering.
you are building a personal knowledge base you will live in daily, you want backlinks, graph view and a huge plugin ecosystem, or you need the same notes on Windows, Linux, iPhone and Android.
At a glance
Twain next to Obsidian on the things that decide it. Every fact is dated against Obsidian's public material.
| Twain | Obsidianverified 20 Jul 2026 | |
|---|---|---|
| Opens a single .md file, in place | Yes | No: a vault is required (planned on their roadmap) |
| Finder Quick Look | Yes (MD + MDX) | No |
| MDX component rendering | Yes: safe, labelled unknowns, never executed | Not natively; plugins only, and the one that renders JSX executes it |
| Content model | Your files, wherever they already are | Plain Markdown files, inside a vault folder |
| Extensibility | No plugin system | 5,867 community plugins and 635 themes, plus 30 core plugins |
| Knowledge tools (graph, backlinks, Canvas, Bases) | No | Yes, all built in |
| Review tooling (diagnostics, anchored notes, rendered diff, AI report) | Yes | No |
| Platforms | macOS 14+ | macOS, Windows, Linux, iOS, Android |
| Runtime | Native macOS app | Electron |
| Price | Free viewer; $19 Pro once (7-day trial) | Free, no account; optional paid Sync and Publish |
Side by side
What Twain has that Obsidian doesn't
- Opens the file already on your disk. No vault, and nothing written into a repo you do not own. Obsidian adds an .obsidian directory to any folder you open as a vault.
- Finder Quick Look for Markdown and MDX: press space on a file and read it rendered, without launching anything.
- Renders MDX natively and safely. Obsidian does not recognise .mdx as a Markdown format at all; with 'Detect all file extensions' on, clicking one hands it to whatever app owns the extension.
- Review tooling built for documentation: diagnostics with source lines, anchored annotations, a rendered diff and a Copy Report for Agent action.
- Edits in place (Pro): a block-based visual editor with in-place table editing, plus folder mode that opens a whole directory with project-wide search and writes nothing into it.
- A native Mac app rather than Electron, which matters most for the Quick Look path where you want a preview instantly.
What Obsidian has that Twain doesn't
- It is free, without limits and without an account. Twain's viewer and review tools are free; the editor and export are a paid upgrade.
- 5,867 community plugins and 635 themes, on top of 30 core plugins. Twain has no plugin system.
- Knowledge tools: graph view, backlinks with unlinked mentions, Canvas on the open JSON Canvas spec, and Bases for database-like views.
- It runs everywhere: Windows, macOS, Linux, iOS and Android, with first-party Sync and Publish available.
- Open formats and a public roadmap.
The vault is the whole difference
Obsidian stores notes as plain Markdown in a folder, but the folder has to be a vault. There is no way to double-click a stray .md in Downloads and have Obsidian show it, and pointing Obsidian at a documentation repo means adopting that repo as a vault, which writes an .obsidian configuration directory into it. Twain has no such concept. It opens the file where it is, shows it rendered, and leaves the folder exactly as it found it. Pro's folder mode does the same for a whole directory, project-wide search included, still without writing anything.
Obsidian agrees this is a gap
This is not us reading a limitation into someone else's design. Obsidian's own public roadmap lists 'Open individual Markdown files: use Obsidian to open .md files outside of your vault' under planned work, and the forum request for it has been open since May 2020, tagged valuable, with later requests merged into it as duplicates. It is planned, not shipped, and there is no date. If it ships, we will update this page and say so.
MDX, and why the plugin route is a trade
Obsidian's accepted file formats do not include .mdx, so by default an MDX file does not appear in the file explorer. Community plugins exist, but the two that treat MDX as text were last touched years ago, and the one that does render JSX does it by compiling and executing the file's JavaScript in a sandboxed iframe, behind a consent prompt, with its own documentation warning that outbound network requests are still possible and to preview only files you trust. That is the precise trade Twain refuses to make: known components become real UI, unknown ones become labelled placeholders, and nothing in the document is ever executed.
Questions
Can Obsidian open a Markdown file that is not in a vault?
Not today. Obsidian requires a vault, and opening an individual file outside one is listed on its public roadmap as planned rather than shipped. Twain opens any .md or .mdx file directly, with no vault and no setup.
Does Obsidian support MDX?
Not natively. The .mdx extension is not among Obsidian's accepted file formats, so those files are hidden by default and open in another app when clicked. Community plugins can render MDX, but the one that renders JSX executes the file's JavaScript. Twain renders MDX components without executing anything.
Does installing Obsidian give me Markdown previews in Finder?
No. Obsidian ships no Quick Look extension, so pressing space on a .md file in Finder gets you nothing from it. Its Page preview feature is an in-app hover preview only. Twain installs a Quick Look extension for both Markdown and MDX.
Is Twain an Obsidian alternative?
For reading, reviewing and editing individual files, yes. A knowledge base is a different job: Obsidian is free, cross-platform and extensible through plugins, and Twain does not build a graph of your notes. The case for Twain is specific: opening a file from Finder with no vault, previewing it with the spacebar, rendering MDX safely and editing in place. The two also run happily side by side on the same files.
Verification date shown reflects Obsidian's public material as of that day; capabilities and prices can change. Twain facts describe what the app does today; see the full comparison tables and all comparisons. Prices are in USD.
Try Twain
The free viewer, with a 7-day Pro trial built in.
Not shipped yet. The signed, notarised build is in progress; the download and checkout open together when it's ready.