To the uninitiated, a Resilio Sync Key (technically a "secret") looks like a password. It functions like one, too, but with a distinct difference. A password grants access to a static location; a Sync Key grants access to a living, breathing directory.
When a user selects a folder on their computer to share, Resilio generates a unique hash. This hash acts as an address and an encryption key combined. When you input that key into a second device—be it a laptop, a phone, or a server two thousand miles away—that device knows exactly where to look for the source files and how to decrypt them.
There are generally two types of keys you will encounter:
No – you must create a new shared folder and re-add all peers with the new key.
The Resilio Sync key is a powerful, decentralized access token that replaces usernames, passwords, and cloud servers. It gives you direct, encrypted, P2P control over your data—but with that power comes responsibility. Treat read/write keys like the master password to your digital vault, and use read-only or encrypted keys whenever possible for external sharing.
Remember: The key is the permission. Lose it or leak it, and you’ve lost control of that folder forever. resilio sync key
Want to generate a test key safely?
Install Resilio Sync in a sandbox or VM, share an empty folder, and experiment with different key types before using real data.
These are alphanumeric strings generated by Resilio Sync to identify specific folders and manage access between peers.
Structure: Keys consist of capital letters (A–Z) and numbers (2–7). They typically contain a 1-character prefix followed by a 32-character Base32 encoded sequence. Key Types by Prefix: A or D: Read/Write keys. B or E: Read-Only keys. F: Encrypted Read-Only keys. C: One-time use keys.
Security: Data is encrypted end-to-end using AES-128. Resilio’s infrastructure cannot see or access your files because the keys are known only to the peers. 2. License Keys
These are files or codes used to activate Pro, Business, or Family versions of the software. Understanding the Sync Encrypted Folder | Resilio Blog To the uninitiated, a Resilio Sync Key (technically
A Resilio Sync key (formerly known as a "secret") is a unique, alphanumeric string used to link folders across different devices without relying on third-party cloud storage. Because Resilio Sync uses peer-to-peer (P2P) technology, these keys act as the essential bridge that allows your devices to find and securely communicate with each other. Types of Resilio Sync Keys
Resilio Sync utilizes different key types to manage how data is accessed and shared. You can identify the key type by its first letter:
Read-Write Key (Starts with 'A'): Grants full access to sync, add, modify, or delete files within a folder.
Read-Only Key (Starts with 'B'): Allows a device to download files but prevents it from uploading changes back to other peers.
Identity Key (Starts with 'M'): Used for "Linking My Devices," allowing all your folders to automatically sync across your own hardware without needing individual folder keys. Remember: The key is the permission
Encrypted Key (Starts with 'F'): Typically used for untrusted nodes (like a rented server). The device can store and seed data but cannot decrypt filenames or file content.
One-Time Use Key: A temporary key that expires after a single use or a set time, enhancing security for one-off shares. Folder Share Keys vs. License Keys
It is important to distinguish between folder-specific keys and license keys: File Sync with Resilio
While you cannot recover a lost key, Resilio allows you to backup your entire identity. Go to Preferences > Advanced > Backup identity. This saves all your active keys and settings. If your hard drive crashes, restoring this backup allows you to reclaim your shared folders without generating new keys.
| Feature | Description |
| :--- | :--- |
| One-Click Sharing | Copy the key (e.g., B7SRV7RFX3S3DZYG42ZYJWW6CBR56RF3X) and send it via any channel—email, SMS, Slack, even a sticky note. |
| Read-Only Keys | Generate a separate, read-only key for viewers. The original key remains read-write. |
| Encrypted Keys | Share an "encrypted key" (.sync file) that lets peers store encrypted backups on an untrusted server without ever seeing the plaintext key. |
| Expiring Keys | Set time-to-live for temporary access (e.g., 24-hour key for a contractor). |
| QR Codes | Mobile apps can scan a QR code of the key—perfect for in-person transfers. |
Because Resilio Sync uses P2P technology (specifically the libtorrent protocol), your key is never stored on Resilio's servers. Resilio offers a Relay Server (for devices behind strict firewalls that cannot do NAT traversal). When a relay is used, the data is temporarily cached but is encrypted end-to-end. The relay server cannot read the key or the data.