Skerry

Your notes. Your files. Your key.

A Markdown notebook for Mac. Your notes stay plain files in a folder you pick, and the ones that matter can be sealed.

Download for Mac brew install --cask dcadolph/tap/skerry

Free and open source · macOS 14 or later · Signed and notarized

Skerry is early and changes often. Keep your own backups.

An illustration of the window layout. Screenshots are on the way.

A calm place to write.

The editor highlights Markdown as you type and hides the syntax away from the cursor, so prose reads clean while the markers stay editable.

Linked notes

Write [[note name]] to link a note. Following a link to a note that does not exist yet creates it, and a backlinks bar lists every note that points here.

Lists, tasks, and tables

Lists continue on Return, task boxes strike through when done, and table columns line up on their own.

Find anything fast

Full-text search on a local index, and a command palette that jumps to any note by fuzzy title.

Your notes are just files.

A library is any folder you pick. Notes are .md files, folders are folders, and pasted images land in assets/ with relative links. Edit a file in another editor and Skerry picks it up within about a second.

Readable without Skerry

Delete the app and your unsealed notes are still there, readable in any text editor. Sealed notes stay ciphertext until Skerry or another reader of the documented format opens them with your key.

Bring your old notes

Import from Bear, Obsidian, Apple Notes, Evernote exports, or plain Markdown. Inline tags become real tags.

Storage you own

Sync through WebDAV, S3, or any folder, sealed before upload. iCloud Drive, Syncthing, or a NAS share work too.

One note, sealed when you choose.

Set a passphrase once, then seal any note from its menu. The file stays where it was, and everything inside it becomes ciphertext.

Private thoughts.mdUnsealed
---
title: Private thoughts
tags: [journal]
---

# Private thoughts

Things I am not ready to say out loud.

A normal Markdown file, readable in any text editor.

7A0E38D2-4CBB-4E30-9A57-2A9F3D1B6C11.mdSealed
---
id: 7A0E38D2-4CBB-4E30-9A57-2A9F3D1B6C11
encrypted: true
encv: 2
---

q3Jb9Ul0aZ2f8rT1nKx4cWv7Hs0dLmEo
P5yGtR2uVb8jQw6Nz1AeYk3Fi9ScXhDp

Title, tags, dates, and body are encrypted. The file name gives nothing away.

Standard cryptography

AES-256-GCM under a random master key, wrapped by a key stretched from your passphrase with Argon2id. A tampered note fails to open instead of opening wrong.

Touch ID and the Keychain

The passphrase lives in the Keychain and is released only after you authenticate. A one-time recovery code is a second way in.

Open to inspection

The code is Apache 2.0, the format is in FORMAT.md, and the threat model says what Skerry protects and what it cannot.

Always at hand.

Capture without opening the app, and let the rest of your Mac reach your notes.

Menu bar capture

Type a thought into the menu bar and save it as a note without bringing the app forward.

Shortcuts and Siri

Create Note, Append to Note, and Search Notes as actions for your automations.

On-device summaries and tags

On Macs with Apple Intelligence, summarize a note and get tag suggestions. Nothing leaves the Mac.

Export anything

Markdown, plain text, HTML, Rich Text, or PDF.

Version history

Browse earlier versions of a note and restore any of them.

Snapshots and a real Trash

Browsable or encrypted backups, and a Trash that keeps deleted notes for thirty days.

Security details.

For people who want to know exactly what happens to their notes.

Nothing left in the clear

Sealed notes stay out of the search index, and backups and sync objects are encrypted before upload under opaque names.

Locks that close

Per-note locks, auto-lock timers, a privacy cover in the app switcher, and copied text that leaves the clipboard after a minute.

Cheap passphrase changes

Changing your passphrase re-wraps the master key, so no note has to be re-encrypted. ChaCha20-Poly1305 is available as a choice.

Checked against the spec

The Argon2id implementation is gated on the RFC 9106 test vectors, and the cryptographic core ships with its tests.

Decoy and self-destruct

An optional decoy passphrase opens a separate, innocent library. Another option erases this device's vault key after repeated wrong guesses.

Where Skerry fits.

Obsidian and Bear are excellent, and for most people either one is the right choice. Skerry covers a narrower need: Markdown notes that are encrypted on disk by software you can read.

They are better at a lot

Plugins, themes, mobile apps, polish, sync services, and years of community work. Skerry has none of that depth, and it is early.

Who it is for

People who want each note sealed, titles and tags included, with open code and a documented format, on storage they control.

What you give up

There is no iPhone or iPad app yet, no plugin system, and the app changes often. Keep your own backups.

Cheap to try, easy to leave

Skerry imports Obsidian and Bear notes, and unsealed notes stay plain Markdown you can take anywhere.

Get Skerry.

Version 0.24.1, free under the Apache 2.0 license with no paid tier. Signed with a Developer ID and notarized by Apple. Requires macOS 14 or later.

Download for Mac brew install --cask dcadolph/tap/skerry

To build it yourself you need Xcode and XcodeGen. The steps are in the README. The iPhone and iPad app is not available yet.