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Encrypt and decrypt text using AES (Advanced Encryption Standard) algorithm with various key sizes and modes.
AES (Advanced Encryption Standard) is the symmetric block cipher that secures most of the modern internet, from HTTPS traffic to encrypted disks and messaging apps. This tool encrypts and decrypts text with AES in CBC mode using PKCS7 padding, and lets you choose a 128-, 192-, or 256-bit key. The same passphrase that encrypts a message is the only thing needed to decrypt it, which is what makes AES symmetric.
Everything happens locally in your browser. Your passphrase is never used directly as the AES key — instead it is stretched into a key with PBKDF2 (SHA-256, 250,000 iterations) over a fresh random salt, which makes brute-forcing a stolen ciphertext dramatically slower. A new random salt and initialization vector are generated for every encryption, so encrypting the same text twice produces different output, and both values are prepended to the ciphertext before it is Base64-encoded. Nothing you type is uploaded, logged, or stored.
Because the salt and IV are embedded in the Base64 output, decryption only needs the passphrase and the matching key size — you do not have to track those values separately. AES-CBC provides confidentiality but not authentication, so it will not detect deliberate tampering with the ciphertext. For high-stakes or regulated data, use a vetted library with authenticated encryption such as AES-GCM. Treat this tool as a convenient, private way to encrypt text for personal use and learning.
256-bit is the recommended default and is the standard for high-security use. 128-bit is still considered strong and slightly faster, but with modern hardware there is little reason not to use 256-bit.
No. A fresh random salt and IV are generated for each encryption and prepended to the ciphertext, so the Base64 output already contains everything decryption needs besides your passphrase.
No. Key derivation, encryption, and decryption all run in your browser with JavaScript, so neither the passphrase nor the plaintext ever leaves your device.
No. The passphrase and key size are the only way to derive the key, and there is no recovery mechanism. If they are lost, the ciphertext cannot be decrypted.
AES itself is the modern standard, but CBC mode provides confidentiality without authentication, so it cannot detect tampering. For regulated or high-stakes data, use an audited solution with authenticated encryption such as AES-GCM.