AES-256 Decryption Tool

About AES-256 Decryption Tool

This is the companion tool to the AES Encryption Tool — paste the Base64-encoded encrypted text along with the exact passphrase used to encrypt it, and the original plaintext is recovered instantly, entirely inside your browser.

Because the encryption uses AES-256 in GCM mode (authenticated encryption), decryption doesn't just reverse the cipher — it also verifies the data hasn't been tampered with or corrupted along the way. If the passphrase is wrong, or the encrypted text has been altered even slightly, decryption fails cleanly with a clear error rather than silently producing garbled or incorrect output.

The passphrase is run through the same PBKDF2 key-derivation process used during encryption (250,000 iterations, using the salt embedded in the encrypted data) to reconstruct the exact same encryption key — this only works if the passphrase is character-for-character identical to the one originally used.

This is useful for recovering text you encrypted earlier with the AES Encryption Tool, decrypting a message someone shared with you along with a separately-communicated passphrase, and verifying that an encrypted payload hasn't been corrupted or tampered with in transit.

How it works

1. Paste the encrypted text. The Base64-encoded output from the AES Encryption Tool.
2. Enter the exact passphrase. Must match the original encryption passphrase precisely.
3. Decrypt. The original plaintext is recovered instantly, or a clear error is shown.