AES Encrypt / Decrypt
Free online AES symmetric encryption with CBC/ECB/CFB/OFB/CTR modes, 128/192/256-bit keys and multiple paddings. Runs entirely in your browser.
Runs locally · data never uploaded
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How to use
What it does
AES (Advanced Encryption Standard) is the most widely used symmetric block cipher — the same key encrypts and decrypts. This tool exposes every common knob: mode (CBC/ECB/CFB/OFB/CTR), key length (128/192/256), padding (Pkcs7/Zero/Iso97971/NoPadding) and output format (Base64/Hex), all computed in your browser.
Example
Key 0123456789abcdef (16 bytes = AES-128), IV abcdef0123456789, plaintext Hello, AES!, mode CBC, padding Pkcs7, output Base64:
KkLrlBZkl1QpvMzKVbrEkg==Switch "Output" to Hex for 2a42eb941664975429bcccca55bac492. After encrypting, hit "Swap" and switch the direction to decrypt to recover the original text.
Modes & padding
- Every mode except ECB needs a 16-byte IV.
- With NoPadding the plaintext must be a multiple of 16 bytes.
- Encryption and decryption must use identical mode, padding, key and IV.
FAQ
Q1.AES-128, 192 or 256?
They differ only in key length — longer is safer and slower. 128-bit is plenty for everyday use; 256-bit is chosen for high-assurance compliance. Keep the key secret in every case.
Q2.CBC vs ECB?
CBC adds an IV so identical plaintexts become different ciphertexts and is far safer. ECB has no IV, so equal blocks produce equal ciphertext and leaks patterns — avoid it for real data.
Q3.Why do I get garbage after decrypting?
Almost always a mismatch in key, IV, mode or padding. Ensure both ends match exactly; with NoPadding also make sure the plaintext is a multiple of 16 bytes.
Q4.Is my data uploaded?
No. Encryption runs in JavaScript inside your browser; the tool works offline and the key stays on your device.
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