# Subfile

> Password-protect and hide photos, documents and videos in an encrypted drive on your Mac. Works offline — no account, no cloud, no subscription. $29 once.

Subfile is a privacy application for macOS. It creates a password-protected
encrypted drive for private files — photos, videos, documents, anything — that
can either stand on its own or be written inside an ordinary carrier file such
as a video, photo or audio file. The carrier keeps opening and playing normally.

## What it is for

- Password-protecting a folder on a Mac, which macOS itself has no built-in way to do
- Hiding files, photos and videos from anyone else who uses the same computer
- Encrypting documents locally, without a cloud service or an account
- Keeping a portable encrypted vault on a USB drive or external disk

## How it differs from the alternatives

- **FileVault** encrypts the whole disk and protects a Mac that is lost, stolen
  or powered off. It does nothing once you are logged in. Subfile works at
  the file level: the vault stays sealed on an unlocked machine.
- **Encrypted disk images (.dmg)** are the closest built-in equivalent, but they
  are clumsy to resize and to keep working inside day to day.
- **VeraCrypt** is powerful and cross-platform, but on macOS it needs macFUSE and
  a security exception, and it has no mobile client.
- **Cryptomator** is built around encrypting folders before they sync to a cloud
  provider. Subfile is local-only by design.
- **Encrypted ZIP / 7-Zip** encrypts an archive, not a working set: every edit
  means extract, change, re-compress.

## Technical facts

- Cipher: XChaCha20-Poly1305 authenticated encryption
- Key derivation: Argon2id (128 MiB memory, 4 iterations, 1 lane)
- Key separation: HKDF-SHA-256 for footer, manifest and per-entry keys
- Integrity: 1 MiB independently authenticated chunks, SHA-256 plaintext digest per file
- Filenames, folder structure, timestamps, sizes and MIME types are encrypted
- No network requirement, no account, no telemetry
- The container format is documented publicly and a reference reader is open source
- No independent security audit has been completed. It does not provide
  VeraCrypt-style hidden-volume plausible deniability, and it is not
  steganography: the encrypted container is appended to the carrier and is
  detectable as high-entropy data.

## Pricing

One-time purchase, no subscription. Personal $29. Universal
$49, which covers the Windows and Linux builds when they ship.
A free tier is included.

## Platforms

macOS ships today. Windows and Linux builds are in progress — the core is
written in Rust and is portable. iOS and Android are planned.

## Pages

- [Home](https://subfile.app/): what Subfile is, how it works, security model, pricing
- [Blog](https://subfile.app/blog): engineering and threat-model notes
- [RSS feed](https://subfile.app/blog/feed.xml)

## Writing

- [Threat modelling for freelancers and small studios on a shared Mac](https://subfile.app/blog/threat-modelling-on-a-shared-mac): A practical threat model for freelancers and small studios: who realistically sees your client files on a shared or borrowed Mac, which risks are worth mitigating, and where an encrypted vault helps.
- [XChaCha20-Poly1305 and Argon2id, in plain language](https://subfile.app/blog/xchacha20-poly1305-and-argon2id): A plain-language explanation of the two primitives behind a Subfile vault: XChaCha20-Poly1305 for encrypting and authenticating data, and Argon2id for turning a password into a key an attacker cannot cheaply guess.
- [Choosing a carrier file: why video beats photos for large vaults](https://subfile.app/blog/choosing-a-carrier-file): How to pick the file that carries your encrypted volume: why video handles large vaults convincingly, where photos stop behaving like photos, and which everyday operations quietly destroy a carrier.
- [What a hidden volume actually protects you from](https://subfile.app/blog/what-hidden-volumes-protect-you-from): An honest account of what an encrypted volume hidden inside an ordinary media file protects against — casual discovery, shoulder surfing, shared machines — and the situations where it buys you nothing at all.

## Frequently asked

- **Is there a subscription?** No. You pay once and the version you bought keeps working, offline, with no licence server to call home to. If a paid 2.0 ever happens, it will be an upgrade you can decline.
- **What happens if I forget my password?** The vault is unrecoverable. There is no reset link, no recovery key escrow and no support ticket that can help — that absence is exactly what makes the encryption meaningful. Keep the password somewhere you trust and keep a backup of the carrier file.
- **Can I open a vault without Subfile?** Yes. The container format is documented publicly and a reference command-line reader is open source, so your files never depend on this app continuing to exist.
- **Does the carrier file still work normally?** Yes — it plays, previews and opens exactly as before, and you can copy, rename, move or back it up freely. What breaks a vault is re-encoding: recompressing a photo, transcoding a video or repacking an archive rewrites the bytes the vault lives in.
- **How is this different from FileVault?** FileVault encrypts the whole disk, which protects a Mac that is lost, stolen or powered off. Once you log in, every file on it is readable by anyone at the keyboard. Subfile works at the file level: the vault stays sealed while you are logged in and opens only when you type its password. The two are complementary, not alternatives.
- **Is hiding a folder the same as protecting it?** No. A hidden folder on macOS — a leading dot, or chflags hidden — is revealed by pressing Command-Shift-Period in Finder, and any backup or search tool reads it normally. Hiding changes what is displayed; encryption changes what is readable.
- **Why macOS only?** macOS shipped first. The core is written in Rust and is portable, so Windows and Linux builds are in progress and are covered by the Universal licence. Mobile apps come after that.
- **What do you collect?** Nothing. No account, no email required to run the app, no analytics enabled by default. Turn off networking entirely and every feature still works.

## Optional

- [Full text of every page](https://subfile.app/llms-full.txt)