AES-256 Encryption Tool
Encrypt or decrypt text with AES-256-GCM using a password. The key is derived with PBKDF2 and everything happens in your browser via the Web Crypto API.
What Happens When You Click Encrypt
- A random 16-byte salt is drawn from your browser's CSPRNG - So the same password never produces the same key twice.
- PBKDF2-SHA256 runs 310,000 rounds, stretching your password + salt into a 256-bit key. On your machine that takes a fraction of a second; for an attacker it multiplies every single guess by 310,000 hash operations.
- A random 12-byte nonce is drawn for AES-GCM - Never reused, which is the one rule GCM cannot survive breaking.
- AES-256-GCM encrypts and signs in one pass, producing ciphertext plus a 16-byte authentication tag.
- Everything self-contained: the output is
AES256GCM.+ Base64(salt · nonce · ciphertext+tag) - One string that carries its own decryption parameters (but never the key).
Decryption runs the pipeline backwards. If even one bit of ciphertext was altered - or the password is wrong - The GCM tag check fails and you get a clean error instead of corrupted output. That authentication step is what separates modern encryption from the ECB-mode examples in old tutorials.
Understanding AES-256 Encryption
What this tool does
Your password is stretched into a 256-bit key with PBKDF2-SHA256 (310,000 iterations) and a random salt, then your text is encrypted with AES-256-GCM - The same authenticated-encryption mode used by TLS, Signal and modern password managers. The output bundles salt + nonce + ciphertext as Base64, so the same tool can decrypt it later with the right password.
Because GCM is authenticated, tampered ciphertext or a wrong password fails loudly instead of producing garbage. Read the plain-English explainer: AES-256 explained simply.
AES-256 in practice
- The strength of the ciphertext is capped by your password - Generate a strong random password or a passphrase for the key.
- Nothing is uploaded: encryption runs in the Web Crypto API on your device.
- Losing the password means losing the data - There is no recovery.
- For storing many secrets, an encrypted vault like the Password Wallet (which uses this same AES-GCM construction) is more practical.
- Curious how encryption differs from hashing? See hashing vs encryption.
How to Use the AES-256 Encryption
Type or paste your text
Anything up to a few hundred kilobytes - Notes, keys, config snippets.
Choose a strong password
The ciphertext is only as strong as this password - Generate one rather than inventing one.
Encrypt and share the output
The Base64 blob bundles the salt and nonce; it's safe to email or store anywhere.
Decrypt with the same password
Paste the blob back, switch to Decrypt, and the exact original text returns - Or a clear error if the password is wrong.
AES key sizes - Why 256 is the standard for new systems
| Variant | Key size | Rounds | Keyspace |
|---|---|---|---|
| AES-128 | 128-bit | 10 | 3.4 × 10³⁸ - Still unbreakable by brute force |
| AES-192 | 192-bit | 12 | 6.3 × 10⁵⁷ |
| AES-256 | 256-bit | 14 | 1.2 × 10⁷⁷ - Comfortable margin even against future quantum attacks |
AES-256 Encryption - FAQ
Has AES-256 ever been cracked?
What's the weak point, then?
What does GCM add over plain AES?
Can you recover my data if I forget the password?
More questions about passwords and security? Browse the security guides.
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