About the AES Encrypt
AES is the encryption standard used by governments, banks and nearly every secure app. This tool encrypts text with AES right in your browser. The simple way is a passphrase: the key and IV are derived from it with a random salt, and the result is Base64 in the same Salted__ format as CryptoJS and the openssl command line, so other tools can decrypt it. For developers there is also a key-and-IV mode with AES-128, 192 or 256 in CBC, GCM, CTR, ECB, CFB or OFB, with PKCS#7 padding and Base64 or hex output. Nothing you type is sent anywhere.
Updated October 2026
How to use the AES Encrypt
- 1Choose Passphrase, or Key and IV for full control.
- 2Enter a passphrase, or a hex key and IV (New key and New IV make random ones).
- 3For key mode, pick the cipher mode and output format.
- 4Type or paste the text to encrypt.
- 5Copy the encrypted result and share the passphrase or key separately.
Passphrase or raw key?
Use a passphrase when a person will decrypt the message with a tool like this one, CryptoJS or OpenSSL. Use a raw key and IV when you are matching a program you wrote, a database field or an API that expects a specific mode and format. In raw mode the key length decides the strength: 16 bytes for AES-128, 24 for AES-192 and 32 for AES-256.
Which mode should I pick?
GCM is the modern choice: it encrypts and also adds a 16-byte tag that detects any change to the data. CBC is the most widely supported mode and what most older systems and online tools expect. CTR turns AES into a stream cipher with no padding. ECB encrypts every block separately, so identical blocks give identical output; avoid it except to match an old system.
- GCM: encryption plus tamper detection, 12-byte nonce
- CBC: classic, needs a random 16-byte IV and padding
- CTR, CFB, OFB: stream modes, no padding
- ECB: no IV, leaks patterns, compatibility only
Sharing encrypted text safely
Send the encrypted text and the passphrase or key through different channels, for example the text by email and the passphrase by phone. In key mode, the IV can travel with the ciphertext because it isn't secret; many systems simply put it in front. For GCM, the last 16 bytes of the output are the authentication tag, and the receiver needs all of it.
Limits of browser encryption
This tool is for text and learning. Passphrase mode uses OpenSSL's older MD5-based key derivation for compatibility, which is fast to guess; use a long random passphrase with it. For files, backups or anything long-term, use dedicated software such as 7-Zip with AES-256, VeraCrypt or age.
Phone and computer
The layout stacks neatly on a phone, and the Copy button puts the whole result on the clipboard without selecting it by hand. To keep a passphrase safe before you use it here, try the Text Encryptor for quick notes, or check the key with the Hash Generator.
Features
- AES-128, AES-192 and AES-256
- CBC, GCM, CTR, ECB, CFB and OFB modes
- OpenSSL and CryptoJS compatible passphrase format
- Random key, IV and salt buttons
- Base64 or hex output
- Runs entirely in your browser
Frequently asked questions
Is AES-256 secure?
Yes. AES-256 with a random key has no practical attack. The weak point is usually the key: a short or guessable passphrase can be cracked, so use a long one.
What is the U2FsdGVkX1 at the start of the output?
It is Base64 for Salted__, the OpenSSL header. After it come 8 bytes of random salt and then the ciphertext. CryptoJS and openssl enc use the same layout.
Can I decrypt this with OpenSSL?
Yes. For passphrase mode run: openssl enc -d -aes-256-cbc -md md5 -a -in file.txt, then enter the passphrase. Our AES Decrypt tool also reads it.
Why is the output different every time?
A random salt (passphrase mode) or a new IV makes each encryption unique, so the same message never looks the same twice. That is a security feature.
What is an IV?
An initialisation vector: a random value used with the key so that repeated messages don't produce the same ciphertext. It doesn't need to be secret, but it must be shared with the person decrypting.
Is my text or key uploaded?
No. The encryption code runs on your device. Even so, don't paste real secrets into any website you don't trust.