.C9R file extension
To open .C9R files on Windows, install and open Cryptomator, then add/open the vault folder that contains the .c9r file (the vault is the whole folder structure, not a single file).
To open a .c9r file, open the containing Cryptomator vault in Cryptomator and unlock it with the correct password/key. A .c9r file is encrypted data; it will look like random bytes unless decrypted by Cryptomator.
Last updated: April 29, 2026 · Reviewed by Julian Stricker
Open on your device
Choose your operating system for a dedicated step-by-step opening guide.
How to open .C9R files
Use these platform-specific instructions to open .C9R files safely.
Windows
- Install and open Cryptomator, then add/open the vault folder that contains the .c9r file (the vault is the whole folder structure, not a single file).
- Unlock the vault with the correct password/key and access your decrypted files via the mounted/unlocked vault drive/folder (do not try to open .c9r directly).
- If you received only a single .c9r file, ask the sender for the entire vault folder and confirm which Cryptomator vault format is used.
Mac
- Install and open Cryptomator, then select the vault folder that contains the .c9r file.
- Unlock the vault using the correct password/key and open the decrypted files from the unlocked vault location (Finder), rather than opening the .c9r file itself.
- If you only have a .c9r file without the vault folder structure, request the full vault from the source.
Linux
- Install and open Cryptomator, then point it to the vault directory that contains the .c9r file.
- Unlock the vault with the correct credentials and use the unlocked/mounted view to open the decrypted files.
- If the .c9r file is standalone, obtain the complete vault directory; a single encrypted object is usually not enough.
iOS
- .c9r files are vault internals; on iOS, use Cryptomator to open and unlock the vault container (folder) rather than attempting to open a single .c9r file.
Android
- .c9r files are vault internals; on Android, use Cryptomator to access/unlock the vault (the whole vault folder) instead of opening a single .c9r file.
Security notes
- Treat .c9r as encrypted content: the main risk is data loss if you lose the vault password/key; keep credentials and recovery information safe.
- Do not rename .c9r to another extension expecting it to become usable; the data remains encrypted and may lead you to open it with inappropriate tools.
- Be cautious when obtaining a “vault” from untrusted sources: while .c9r is encrypted data, any software parsing complex formats can have bugs—prefer opening vaults only with the official Cryptomator app and keep it updated.
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Can't open this file?
These are the most common causes and fixes when .C9R files fail to open.
Common reasons
- Trying to open a .c9r file directly shows gibberish or an error
- You only received a single .c9r file
- Vault unlock fails (wrong password/key or mismatched vault format)
Fix steps
- Open the vault (the entire vault folder) in Cryptomator and unlock it to access the decrypted files.
- If you don’t know where the vault is, search for the surrounding Cryptomator vault directory rather than focusing on a single .c9r file.
OS-specific troubleshooting
What is a .C9R file?
.c9r is an extension used by Cryptomator’s vault format for encrypted filenames and file objects stored inside an encrypted vault. Cryptomator encrypts files individually, producing per-file encrypted objects in the vault storage. You normally don’t open .c9r files directly; you unlock/mount the vault and access the decrypted files through Cryptomator.
Background
In practical terms, a .c9r file is not a “standalone document format” intended for interchange. It is usually one piece of a larger Cryptomator vault layout. If you only have a single .c9r file without the rest of the vault structure (or without the correct key/password), you typically cannot recover meaningful plaintext from it.
Common MIME types: application/vnd.cryptomator.encrypted
Further reading
Authoritative resources for more details on the .C9R format.
Common .C9R issues
Trying to open a .c9r file directly shows gibberish or an error
.c9r is encrypted vault data and is not meant to be opened by text editors, media players, or office apps.
- Open the vault (the entire vault folder) in Cryptomator and unlock it to access the decrypted files.
- If you don’t know where the vault is, search for the surrounding Cryptomator vault directory rather than focusing on a single .c9r file.
You only received a single .c9r file
A .c9r file is typically just one encrypted object inside a vault. Without the rest of the vault structure and correct credentials, it is usually not usable.
- Ask the sender for the complete Cryptomator vault folder (all files/folders that belong to the vault), not just one .c9r file.
- Confirm you also have the correct password/key required to unlock the vault in Cryptomator.
Vault unlock fails (wrong password/key or mismatched vault format)
If credentials are incorrect or the vault was created with a different configuration/format, Cryptomator cannot decrypt the contents.
- Verify you are using the correct password/key and the correct vault folder (not a copied subset).
- If the vault was moved or synced, ensure the entire vault content is present and consistent before trying again.
FAQ
What program opens .c9r files?
.c9r files are associated with Cryptomator vaults. You open them by opening/unlocking the vault in Cryptomator, not by opening the .c9r file directly.
Is .c9r the encrypted version of my original file?
In Cryptomator vaults, encrypted objects commonly use .c9r. The original file is accessible after you unlock the vault in Cryptomator.
Can I decrypt a .c9r file without Cryptomator?
In normal use, you should decrypt/access it through Cryptomator by unlocking the vault. A single .c9r file by itself is typically not sufficient without the full vault context and correct credentials.
What is the MIME type for Cryptomator-encrypted content?
A registered vendor media type used for Cryptomator-encrypted content is application/vnd.cryptomator.encrypted.
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