AES GCM File Encrypt Decrypt
Encrypt or decrypt files with AES-256-GCM and a passphrase in your browser. PBKDF2 key derivation, no uploads to a server.
Encrypt and decrypt files with AES-256-GCM in the browser
AES-GCM (Galois/Counter Mode) provides authenticated encryption: ciphertext is protected against tampering
as well as disclosure. This tool derives a 256-bit key from your passphrase with PBKDF2-SHA-256
(600,000 iterations), encrypts the uploaded file locally, and downloads an .omt1.enc container.
Decrypt mode reverses the process when you supply the same passphrase.
File format (OMT1)
Encrypted downloads use a small binary header (magic bytes OMT1, version, iteration count, salt,
IV) followed by the AES-GCM ciphertext. Keep the passphrase secret; without it the payload cannot be recovered.
For text-only AES workflows see Encrypt Decrypt, and for raw key derivation parameters try PBKDF2 Key Derivation.
Frequently Asked Questions
Are files uploaded to OnlineMiniTools?
No. Encryption and decryption use the Web Crypto API in your browser; file bytes never leave your device.
What happens if I lose the passphrase?
The ciphertext cannot be decrypted. Store passphrases in a password manager or escrow them through your organization’s normal secret-handling process.
Is there a size limit?
Yes. Very large files may exhaust browser memory; the tool enforces a 25 MB limit per operation.
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