fa.to
hello@fa.to
Client-side encrypted

DOCUMENTATION

Set up your vault.
Keep hold of the keys.

Start with managed fa.to storage or connect an ordinary SFTP account. These guides explain the choices, the important recovery steps and what to check when a connection fails.

01 · START HERE

Choose how your vault is hosted

Managed fa.to vault

Choose a plan on the Hosted page, verify your email and select an available region. When provisioning finishes, open fa.to on Android, choose Log in with fa.to and approve the connection shown in the app.

Your own SFTP storage

Choose Add your own SFTP server in the app. You need a hostname, port, username, password or private key, and preferably the server's SHA-256 host-key fingerprint. No fa.to account is required.

02 · DESKTOP SEEDING

Upload a folder with fatod

The experimental fatod utility can seed a large local file or complete folder tree into the same encrypted vault used by the Android app. It is an upload tool, not a continuous synchronisation client.

For managed storage, run fatod with --hosted. It opens fa.to in your browser, uses a single-use login tied to that fatod process, and returns the managed connection without displaying or saving its private SFTP key. Your separate vault passphrase is entered locally and is never sent to the website.

Stop uploads in the Android app before starting fatod, and do not let two devices write to the same vault simultaneously.

03 · CONNECTION DETAILS

What each SFTP field means

Connection name
A label used only inside the app, such as “Home server” or “Hetzner”.
Server address
The SFTP hostname supplied by the provider. Prefer a hostname over an IP address because provider IPs can change.
Port
Usually 22. Use another port only when the provider explicitly requires it.
Username and sign-in
The SFTP account name and either its password or a supported private-key file.
Remote folder path
An existing writable folder. Leave it blank to use the account's starting folder. fa.to creates a .fato-v3 directory inside it.
SHA-256 fingerprint
A value published by the provider or administrator that lets the app verify it reached the intended server.

Do not copy a fingerprint from an unexpected connection warning and assume it is safe. Compare it with a value obtained separately from the provider or server administrator.

04 · PROVIDER EXAMPLE

Set up a Hetzner Storage Box

This example uses password authentication on SFTP port 22, which is the simplest setup. fa.to is not affiliated with or endorsed by Hetzner.

  1. 1

    Create the Storage Box

    In Hetzner Console, create a Storage Box and set a strong password. Enable External Reachability if the phone will connect from outside the Hetzner network.

  2. 2

    Copy the connection details

    The main account normally uses username uXXXXX, hostname uXXXXX.your-storagebox.de and port 22. A sub-account has its own username and matching hostname.

  3. 3

    Add it in fa.to

    Choose Add your own SFTP server, enter the hostname, port and username, then select Password and enter the Storage Box password.

  4. 4

    Use the starting folder

    Leave Remote folder path blank unless you deliberately created another writable folder. fa.to will place its encrypted .fato-v3 directory in the SFTP starting folder.

  5. 5

    Verify the server

    Compare the SHA-256 fingerprint with the SSH host-key fingerprints shown in the Storage Box overview. Keep verification enabled and paste the matching value, including its SHA256: prefix.

  6. 6

    Create the vault

    Choose a unique vault passphrase of at least 10 characters, save the recovery file somewhere separate, and connect. Do not rename or edit files inside .fato-v3 using another SFTP client.

Provider references: create a Storage Box · SFTP access · SSH keys

05 · DO NOT SKIP

Passphrases and recovery files

  • The vault passphrase protects the key that decrypts the vault. It is never sent to fa.to or the storage server.
  • fa.to cannot reset a forgotten vault passphrase or reconstruct a lost vault key.
  • A recovery file can unlock the vault without the passphrase. Treat it like a physical spare key and store it offline or in another trusted location.
  • Changing the passphrase re-protects the vault key; it does not re-upload or re-encrypt every stored file.
  • Biometric unlock protects convenient access on that Android device. It does not replace the recovery file.

06 · EVERYDAY USE

Working with files

Uploads

Upload individual files or select a folder to recreate its structure. Larger jobs run in the background with an Android notification, visible progress and a cancel action.

Media

Browse encrypted thumbnails, swipe between images and videos, pinch to zoom into images, and stream compatible video without first exporting a permanent readable copy.

Organisation

Create folders, move or rename items, choose list or thumbnail views, and set the preferred view for all existing and future folders.

Storage

The Storage screen groups recorded file sizes by type, shows the largest files and identifies space still occupied by items in Trash.

Trash

Deleted items remain in Trash for 30 days unless permanently removed sooner. Items in Trash continue to use storage until they are permanently deleted.

Readable copies and thumbnails

Opening or saving a file decrypts a temporary or exported copy on the device. Decrypted thumbnails are cached for faster browsing; clear them manually in Settings, or choose to clear them whenever the vault locks. Protect exported copies using the normal security and backup controls on your phone.

07 · TROUBLESHOOTING

Common connection and upload problems

Host-key fingerprint does not match

Stop and compare the fingerprint with the provider's control panel or another trusted source. Do not disable verification merely to dismiss an unexpected change.

Permission denied or the vault cannot be created

Confirm the username and authentication method, then check that the remote folder already exists and is writable. Try leaving the path blank when the provider starts SFTP inside the account's writable directory.

The storage limit has been reached

Permanently remove unneeded items from Trash or increase the provider/account capacity, then retry the upload. Moving an item to Trash alone does not release its storage.

An upload was interrupted

Open fa.to again and retry the affected upload. The app uses resumable encrypted chunks where possible, while Android still controls when background work may run under battery or network restrictions.

The passphrase and recovery file are both lost

The encrypted vault cannot be recovered. If it is a managed vault, the account dashboard can reset and empty the deployment so you can create a new vault, but the old encrypted files will be permanently lost.

08 · SECURITY OVERVIEW

What the storage server receives

fa.to encrypts file contents in authenticated AES-256-GCM chunks before upload. Filenames, folder information and thumbnails are encrypted too. New and upgraded vault keys use Argon2id to make offline passphrase guessing more expensive.

The server can still observe operational information such as the SFTP account, connection times, network addresses, encrypted object sizes and total storage use. Client-side encryption protects confidentiality, but it does not replace a separate backup or secure the readable copies you intentionally export.