OPFS VFS
A browser filesystem backed by the Origin Private File System, with POSIX-style file operations, write-ahead logging, crash recovery, and shared worker transport.
Use the core API from TypeScript or JavaScript, connect file-backed interfaces with the React SDK, or compose storage through the Effect v4 adapter. Volume Explorer and reusable file previews help you inspect and edit browser-local files. Ordinary filesystem use through the core package has no runtime dependencies.
New mounts default to disk buffering and balanced background synchronization. See storage defaults for save boundaries and switching buffer modes.
Published packages
| Package | Purpose | Documentation |
|---|
| @opfs-vfs/opfs-vfs | Core filesystem, worker clients, and PGlite and just-bash adapters | Core guide |
| @opfs-vfs/plugin-subscriptions | Bounded file-change notifications | Subscriptions guide |
| @opfs-vfs/react | React providers, lifecycle hooks, and subscribed reads, in preview | React SDK guide |
| @opfs-vfs/effect | Effect v4 scoped volumes, FileSystem service, and change streams | Effect adapter guide |
| @opfs-vfs/devtools | Volume Explorer with file actions, a shell, previews, and app debugging | Volume Explorer guide |
| @opfs-vfs/file-preview | Reusable React file previews and a virtualized text editor | File preview guide |
The React SDK preview requires React 19. The Effect adapter requires stable Effect v4, starting at 4.1.0 and excluding v5 and prereleases. Install either one with the exact core and subscriptions versions it lists as peers, and upgrade them together, because their default workers contain a copy of the storage engine. See each package guide for installation and peer dependencies.
The private website workspace contains marketing, docs, demos, and live benchmarks. It consumes the public packages through workspace:*; it is not published to npm. The experimental DuckDB adapter persists analytics databases through OPFS VFS using separately built, compatible DuckDB-Wasm assets.
Development
Use Node.js 22.12 or newer and the pnpm version pinned in package.json.
pnpm install
pnpm --filter @opfs-vfs/opfs-vfs exec playwright install chromium
pnpm build
pnpm typecheck
pnpm test
pnpm lint
pnpm fmt:check
pnpm deadcode
Run pnpm fmt to format files and pnpm duplicates for an advisory duplication report. See development for package commands and API for the library exports.
License
This working tree uses the source-available PolyForm Noncommercial License 1.0.0. It permits noncommercial use, modification, and distribution. Commercial use requires separate permission from the copyright holder. The license is not OSI-approved open source.
See the subscriptions package and subscriptions API for optional live file-change notifications.
