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AES Encrypt / Decrypt

Encrypt or decrypt text using AES-256-GCM. Nothing leaves your browser.

How AES Encrypt / Decrypt works

AES Encrypt / Decrypt uses the browser's native WebCrypto API to encrypt and decrypt text with AES-256-GCM, one of the strongest symmetric encryption algorithms available. You provide a passphrase; the tool derives a 256-bit AES key from it using PBKDF2 with a random salt, then encrypts your text with a random initialization vector. Everything runs on your device using SubtleCrypto; your passphrase and plaintext never leave the browser tab.

One critical point: if you lose the passphrase, the encrypted text is unrecoverable. AES-256-GCM with a properly derived key provides no backdoor, no recovery mechanism, and no master key. Store your passphrase in a password manager alongside the encrypted output if you need to recover it later.

Written by Bastien Sulyan

How to use AES Encrypt / Decrypt, step by step

  1. Type or paste the text you want to encrypt into the plaintext field.
  2. Enter a passphrase in the passphrase field. Use a strong, unique passphrase and store it securely.
  3. Click 'Encrypt' to produce the ciphertext (a base64-encoded string containing the salt, IV, and encrypted data).
  4. Copy the ciphertext and store it alongside your passphrase reference.
  5. To decrypt, paste the ciphertext into the input, enter the same passphrase, and click 'Decrypt'.

Common use cases

  • A developer needs to store a sensitive configuration snippet (API keys, connection strings) in a shared document and encrypts it before sharing.
  • A journalist encrypts a source's contact details before backing them up to a cloud service that the journalist does not fully control.
  • A sysadmin encrypts a temporary password before sending it in a chat message, so the recipient decrypts it using an agreed passphrase.
  • A user wants to store personal notes containing sensitive information in a plain text file, encrypted so the file is safe if the device is accessed by someone else.

Frequently asked questions

What encryption algorithm does this tool use?

AES-256-GCM (Advanced Encryption Standard, 256-bit key, Galois/Counter Mode). The key is derived from your passphrase using PBKDF2-SHA-256 with a random 16-byte salt and 310,000 iterations, which slows brute-force attacks on weak passphrases. A random 12-byte initialization vector is generated for each encryption. The output bundles the salt, IV, and ciphertext as a single base64 string.

Does my passphrase or plaintext get sent to any server?

No. The encryption and decryption use the browser's SubtleCrypto API (window.crypto.subtle), a sandboxed, hardware-accelerated cryptographic engine that operates entirely within the browser process. Nothing you type here reaches Sunasty or any third party. You can verify this by watching the Network tab in your browser DevTools during encryption.

What happens if I lose my passphrase?

The encrypted text becomes permanently unrecoverable. AES-256-GCM with PBKDF2 key derivation provides no recovery path; there is no master key, no hint system, and no server that holds a copy. This is intentional: it is the same property that makes the encryption trustworthy. Always store your passphrase securely before encrypting data you need to access later.

Is AES-256-GCM the same as 'military-grade' encryption?

AES-256 is the standard approved by NIST and used by US government agencies for top-secret data. The 'military-grade' label is a marketing term; the technical fact is that AES-256-GCM is one of the most widely vetted symmetric encryption algorithms and no practical attack against a properly implemented version is known.

Can I encrypt files rather than text with this tool?

This tool encrypts text you type or paste. For file encryption, the approach would need to read the file as an ArrayBuffer and pass it to SubtleCrypto.encrypt, which this tool does not currently do. To encrypt a file, consider using a dedicated tool like Cryptomator (for cloud storage) or GPG on the command line.

Can someone decrypt my ciphertext without knowing the passphrase?

Not in practice. With a strong passphrase and 310,000 PBKDF2 iterations, the computational cost of trying every possible key is prohibitive even for well-resourced attackers. The GCM mode also provides authenticated encryption: any modification to the ciphertext causes decryption to fail, so tampering is detected.