Decrypt AES-encrypted text with the secret key, privately in your browser.
AES Decryption reverses AES encryption: paste the ciphertext, supply the secret key it was locked with, and instantly recover the original readable message. Like the encryption side, every calculation runs inside your browser, so the encrypted data and the key you type are never uploaded, cached, or logged. It is the companion tool you use whenever you receive AES-protected text or need to read something you encrypted earlier.
AES is a symmetric cipher, so the same secret key that locked the data is the only thing that can unlock it. Decryption takes a block of ciphertext plus that key and runs the encryption steps in reverse to reconstruct the original plaintext byte for byte. There is no back door and no way to shortcut the key: this strict dependence on the correct secret is exactly what keeps the message confidential while it travels across untrusted channels.
The tool derives the key from your passphrase, then runs the transformation rounds in reverse — unmixing and substituting bytes — until the original plaintext emerges. If the key is even slightly wrong, the rounds cannot be reversed correctly and you get an error or garbage instead of your message. Because the process is deterministic, the same ciphertext and key always yield the same plaintext, which makes it reliable for verifying encrypted data.
Suppose a colleague sends you this over chat:
U2FsdGVkX1+9Yb3kQ2m8Zr7xnP0aVt6...blue-otter-42Meet me at the cafe at 5pmYou paste the ciphertext, type blue-otter-42, and the original sentence appears. If you mistype the key as blue-otter-43, decryption fails — proof that only the correct key unlocks the data.
If you do not get readable text back, work through the usual causes. First, check the key character by character — AES is case-sensitive and treats extra spaces or a trailing newline as part of the key. Second, make sure you pasted the entire ciphertext; a truncated block cannot be decrypted. Third, confirm the ciphertext was produced by a compatible AES scheme, since different modes and key-derivation settings are not interchangeable. When decryption keeps failing despite a correct-looking key, the most likely explanation is a subtle mismatch in one of these three areas.
Sending ciphertext and its key to a remote server would expose exactly the data you are trying to protect. This tool keeps everything local: no server round-trip, no logging, no account. Close the tab and nothing remains.
The overwhelmingly common cause is an incorrect key. AES requires the exact same secret key that was used to encrypt — check for typos, extra spaces, or case differences.
No. Decryption is performed entirely in your browser; nothing is transmitted.
Without the correct key, AES ciphertext cannot be recovered. Strong encryption is designed so there is no back door — keep your keys safe.
You can decrypt AES ciphertext as long as it was produced with a compatible AES scheme and you have the matching key.
Yes — character for character, including case. Any difference will prevent recovery.
A wrong key can sometimes produce meaningless bytes rather than a clean error; readable output only appears with the correct key.
Yes — re-encrypt the recovered plaintext with the same key using the AES Encryption tool.
Use the AES Encryption tool to create ciphertext, and explore related utilities like the Hex to ASCII Converter for byte-level decoding.
How to Use AES Decryption — Decrypt Text Online
Paste the AES-encrypted text you received or saved earlier.
Provide the exact key used to encrypt the message, matching case and spacing.
The original plaintext appears instantly and can be copied.
Decrypt AES-encrypted text with the secret key, privately in your browser.
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Sep 11, 2026Type:
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