What is AES?
AES (Advanced Encryption Standard) is a symmetric block cipher adopted by NIST in 2001, based on the Rijndael algorithm. It encrypts data in 128-bit blocks using a secret key of 128, 192 or 256 bits, and the same key both encrypts and decrypts. AES is the worldwide standard for protecting data — it secures TLS connections, disk and file encryption, VPNs and messaging apps. Its security depends on keeping the key secret and using a strong mode (such as CBC with a random IV, or authenticated GCM). This tool runs AES entirely in your browser, so your key and plaintext never leave your device.
Private by design: AES encryption runs entirely in your browser — your key and plaintext never leave your device. Keep the same key, mode and IV to decrypt later with the AES Decryption tool.
How AES works
AES is a block cipher that transforms data in fixed 128-bit (16-byte) blocks using your secret key:
- Key expansion — the key (128, 192 or 256 bits) is expanded into a set of round keys.
- Rounds — each block runs through 10, 12 or 14 rounds of SubBytes, ShiftRows, MixColumns and AddRoundKey, thoroughly mixing the data.
- Mode & IV — a mode of operation (CBC, GCM, …) with an initialization vector chains the blocks so identical plaintext does not produce identical ciphertext.
- Output — the result is ciphertext, reversible only with the same key, mode and IV.
How to use
- Enter the text you want to encrypt.
- Provide a key (and IV/mode settings where required).
- The encrypted output is produced in your browser.
- Share the ciphertext; share the key only through a safe channel.
Options explained
- Key size — 128, 192 or 256-bit keys. AES-256 has the largest security margin.
- Mode — CBC, ECB, CFB, OFB, CTR or GCM. Avoid ECB; prefer authenticated GCM, or CBC with a random IV.
- IV (initialization vector) — A random value mixed into the first block so identical messages encrypt differently. Use a fresh IV per message.
- Padding — PKCS7 padding fills the final block to the 16-byte boundary for block modes like CBC.
- Key from passphrase — Optionally derive the key from a passphrase using a salt and iterations instead of a raw key.
Common uses
- Encrypting files, messages and backups.
- Protecting data at rest in apps and databases.
- The symmetric layer inside TLS, VPNs and disk encryption.
- Securing API payloads and configuration secrets.
Frequently asked questions
Is AES secure?
Yes. AES, especially AES-256, is the global standard and has no known practical break when used correctly with a strong key and mode.
What is the difference between AES-128 and AES-256?
The key length. Both are secure; AES-256 uses a longer key for a higher security margin.
What is an IV?
An initialization vector — a random value used with modes like CBC and GCM so that identical messages encrypt differently. Use a fresh random IV for each message.
Is my data sent to a server?
No. Encryption happens in your browser; your key and message stay on your device.
How do I decrypt the result?
Use the AES Decryption tool with the same key, mode, padding and IV.