AES Decryption Online

What is AES decryption?

AES (Advanced Encryption Standard) is a symmetric cipher. This tool lets you decrypt AES ciphertext by providing the key, mode, IV/nonce, padding, and optional GCM authentication tag. Everything runs in your browser.

AES is reversible, so the correct key returns the original plaintext, while MD5 is a one-way hash that no key can undo; the MD5 encrypt and decrypt tool therefore generates a 32-character digest and, in place of decryption, checks whether a candidate string matches a hash you already hold.

How to use the AES decryption tool

• Enter Input: Add your plain text for encryption or your AES-encrypted text for decryption.
• Select Cipher Mode: Choose the AES mode (CBC, ECB, etc.). Use the same mode for decryption that was used during encryption.
• Choose Padding: Pick the padding method required for your operation (must match during decryption).
• Add IV (If Required): Enter the Initialization Vector if your selected cipher mode uses one. For decryption, use the exact IV from encryption.
• Set Key Size: Select the key length (128/192/256 bits). This must match between encryption and decryption.
• Enter Secret Key: Provide the key used for encryption. Use the same key while decrypting.
• Select Output Format: Choose how you want the result displayed - Base64, Hex, or Plain Text (for decrypted output).
• Run the Action: Click Encrypt to generate encrypted output or Decrypt to retrieve the original text.

Supported modes and padding

• CBC: Use a 16-byte IV and PKCS5/PKCS7 padding. NoPadding isn’t supported in WebCrypto.
• CTR: Stream-like; requires a unique 16-byte IV/nonce for every message.
• GCM: Authenticated encryption; needs a 12-byte IV/nonce and an auth tag. Include the tag when decrypting.

Tips for successful decryption

• Match mode, key length, IV/nonce, padding, and tag (for GCM) exactly to the original encryption.
• Verify encodings: ciphertext/IV/tag can be Base64 or Hex—use the correct format switch if available.
• Don’t reuse IVs with the same key; generate fresh IVs per encryption.
• If decryption fails, double-check tag length (GCM) and that the IV is the right size.