OpenSync

End-to-end encrypted sync for your Obsidian vault. Your notes are sealed on your own device before they leave it, so the server stores ciphertext and cannot read a note, a filename, or a folder. Notes sync free and unlimited. Attachments are the paid tier — or free forever on a relay you run yourself.

Status: not yet in the community plugin directory. It is verified working inside Obsidian 1.13.7 by 91 automated assertions that drive the real application, but it has not been reviewed by Obsidian staff and has not been tested on a phone. See Status.

What syncs, and what it costs

Why that line and not another one. A vault of five hundred notes weighs about five megabytes. A vault with a year of screenshots in it weighs gigabytes. Text costs so little to carry that charging for it would be theatre; attachments are the only part that costs real money to keep, so they are the part that is paid for.

Running your own relay unlocks everything, free. What is being sold is not running a server. If you run one, the storage is already yours and there is nothing to charge you for — so the plugin stops metering the moment it is pointed somewhere that is not our relay. That is not an honour system: it reads the relay's hostname. See docs/self-hosting.md.

The file types the free plan carries are md, canvas, base, excalidraw, json, csv, txt, svg, css, yaml, yml, bib, drawio. An Excalidraw drawing is a markdown file, so it syncs. Nothing is ever deleted by a plan: a file the plan does not carry simply stays on the device it is on, and the settings pane lists them by name so you are never guessing.

Install

From the community directory — not yet; see Status.

Beta, from this repository. Install BRAT, then Add beta plugin and give it open-sync/opensync-obsidian.

By hand. Download main.js, manifest.json and styles.css from the latest release into <your vault>/.obsidian/plugins/opensync/, then enable OpenSync under Settings → Community plugins.

Start syncing

The first device

1. Settings → OpenSync.
2. Press Generate beside Vault key, then beside Account key. The relay address is already filled in.
3. Press Recovery kit → Show it, and print the page. Do this now rather than later — see If you lose everything.

That is the whole setup. The status bar reads OpenSync: up to date when the vault has been published.

The second device

On the device that already has the account: Add a device → Show a code.

You get three ways to carry the same pairing, and they are for different situations:

• Scan the QR — for a phone, which is the worst thing to type on.
• Copy the opensync://pair… line — for a second computer, which cannot point a camera at the first one's screen.
• Read the ten characters aloud — for anything else. The relay address has to be typed too in that case, which is the half people get wrong.

On the new device, paste or type it into Join from a code and press Join.

Your vault key is never shown and never typed. It travels sealed under a key derived from those ten characters by a SPAKE2 exchange, so the relay in the middle carries ciphertext and somebody watching the wire at that exact moment gets one guess. A code is spent when it is answered — right or wrong — which is what lets it be short enough to read down a phone line.

What happens when two devices disagree

Nothing is lost. Ever. That is the one rule everything else bends around.

Two devices that edit the same note produce two files: yours keeps its name, and the other becomes note (conflict 2026-09-12 from Laptop).md — named after the device whose version is inside it, so you can tell which is which before deciding. A notice tells you it happened.

A deletion never beats an edit. If one device removes a file while another changes it, the change wins; an unwanted file is a nuisance you fix in a second, and a lost edit is gone.

If you lose everything

There is no password reset, because there is no password and we hold no key. If every device is lost, the only way back into the vault is the recovery kit — a page you print, carrying both keys grouped for typing, each with a checksum, and bound together by a fingerprint so two pages cannot be mixed into an account that owns nothing.

Print it. Put it where the passports are. Not in the vault it unlocks, and not in a photo library that syncs to somebody else's server.

If a device is lost or stolen

Rotate the vault key. It re-seals everything under a new key and sweeps what the old one addressed, after which anything left on a relay is ciphertext nobody holds a key for. This is the only real delete a system like this has: a relay may ignore a deletion request, and anything ever fetched was ever copied.

It costs pairing every device you are keeping, and it always costs that. There is no announcement, because a notice that reached your devices would reach the one you are rotating away from.

One warning the pane also gives you: one key covers every namespace on the account. If the same account also syncs a clipboard or a password store, rotate those from their own apps first — afterwards nothing can.

What this plugin reads

Every file in your vault. It has to: syncing a vault means knowing what is in it. The plugin enumerates the vault on each sync, reads the files it is carrying, and seals them before anything leaves the device. It reads nothing outside the vault, and on the free plan it reads only the file types listed above.

One remote service, and only the one you name. The relay in Settings → OpenSync, which is relay.opensync.network unless you change it. Nothing else is contacted: no analytics, no update check, no telemetry of any kind. Point it at your own relay and this plugin talks to nobody else at all.

An account is needed for the hosted relay, because a relay that serves anonymous keys is a free file host. None is needed to use the plugin against your own.

What the server knows

Two hashes make that hold. A blob's address is the SHA-256 of its ciphertext; the integrity check inside the sealed manifest is a BLAKE3 of the plaintext. Addressing by the plaintext hash would deduplicate across accounts and hand anyone with a copy of a suspected file a way to ask the server whether you have it.

More in docs/security.md.

Documentation

• Testing on real devices — getting a build onto a Mac, an iPad and a phone over a tailnet, and what to try once it is there.
• Running your own relay — the long version: build, TLS, admission, backups, and pointing the plugin at it.
• Troubleshooting — what each failure actually means, including the ones that look like something else.
• Security model — what is protected, what is not, and the decisions behind both.

Status

Verified inside Obsidian 1.13.7 on macOS by 91 automated assertions that drive two real copies of the application over the remote debugger — pairing, rotation, the recovery kit, conflict handling, 504 files published in 2.8 s and fetched in 1.5 s, and zero plaintext in the relay's own storage.

Not yet done, and honest about it:

• Not tested on a phone. The manifest claims mobile support and the code has mobile-specific paths, but nothing has run there yet.
• Not reviewed by Obsidian staff, and not in the community directory.
• No version history. A superseded version of a note is not kept.
• A rename is a delete and a create, so moving a large folder republishes everything in it. Correct, and expensive.
• The merge is whole-file. Two people editing different paragraphs of one note produce a conflict copy, not a merged note.

Building from source

git clone https://github.com/open-sync/opensync-obsidian.git
cd opensync-obsidian
npm install
npm run build
npm run typecheck

That is the whole thing — one repository, no toolchain beyond Node. The build is reproducible: a clean checkout produces a main.js byte-identical to the one attached to the release.

The plugin is built on OpenSync, an end-to-end encrypted sync engine that lives in its own repository. Its browser client is vendored here, under vendor/opensync-client/, copied verbatim by npm run vendor. That copy is why this repository builds alone, and npm run vendor:check — which the test suite runs — fails if it has drifted from the engine.

vendor/opensync-client/wasm/inline.ts is the compiled Rust core as base64. It is generated, not written, and its source is the opensync-* crates in the engine repository. To rebuild it you need the engine checked out beside this repository and a Rust toolchain:

npm run wasm         # recompile the core to wasm, then re-vendor

main.js is the built plugin and is not in version control. To build one that points at your own relay, or at none:

OPENSYNC_HOSTED_RELAY=wss://relay.example.net/ npm run build
OPENSYNC_HOSTED_RELAY= npm run build

Running the checks

cargo build --release -p opensync-relay --manifest-path ../opensync/Cargo.toml
npm run check:all

Three suites, all of which drive the real application rather than standing in for it. Each starts its own relay on a port the OS hands out, builds vaults under a temporary directory, and gives each Obsidian its own --user-data-dir — so they never touch the Obsidian you use, and running them while it is open is fine.

License

MIT. See LICENSE.

The engine this is built on is dual-licensed under MIT or Apache-2.0; MIT is the option taken here, so the two agree.