What is AES-256 encryption?

AES (Advanced Encryption Standard) with a 256-bit key is the gold standard for symmetric encryption. It is used in HTTPS, disk encryption, VPNs and virtually all secure systems. AES-256 is considered computationally unbreakable with current technology.

What does GCM mode add?

Galois/Counter Mode provides authenticated encryption. It encrypts the data AND produces a MAC that detects any tampering. If the ciphertext is altered even slightly, decryption fails — you know the data has been corrupted or tampered with.

Is this tool safe for sensitive data?

It runs entirely in your browser using the Web Crypto API — nothing is sent to a server. For critical production secrets, use a dedicated key management system (AWS KMS, HashiCorp Vault) with proper access controls.

What is the difference between encryption and hashing?

Encryption is reversible with the correct key — you can get the original data back. Hashing is one-way — you cannot reverse it. Use encryption when you need to store and retrieve a secret; use hashing (bcrypt, Argon2) for passwords.

How strong is my passphrase?

The passphrase is the weakest link. AES-256 is unbreakable, but a short or common passphrase can be guessed. Use a passphrase of at least 16 random characters, or a sequence of 5+ random words for best security.

Can I decrypt the output on another device or in code?

Yes, as long as you use AES-256-GCM with PBKDF2-SHA-256 key derivation and the same salt/IV values included in the ciphertext output. The Web Crypto API implementation is standard and interoperable with other AES-GCM libraries.

🛡️

Encryption / Decryption

Encrypt and decrypt text with AES-256. Runs entirely in your browser — no data ever leaves your device.

💻 Developer Tools Free Browser-based

Tool

Plaintext

Secret key (passphrase)

What Is AES Encryption?

AES (Advanced Encryption Standard) is the world's most widely used symmetric encryption algorithm. It was selected by NIST in 2001 after a five-year competition and is now used in everything from HTTPS connections to encrypted hard drives. This tool uses AES-256 — a 256-bit key — which provides 2²⁵⁶ possible keys. No known attack can break AES-256 with current technology; brute-forcing it would take longer than the age of the universe. Your passphrase is stretched into a 256-bit key using PBKDF2 with SHA-256 and a random salt, so even a short passphrase produces a strong key.

How AES-256-GCM Works

GCM (Galois/Counter Mode) is an authenticated encryption mode that does two things at once: it encrypts your data (confidentiality) and produces a MAC (message authentication code) that verifies the data has not been tampered with (integrity). If the ciphertext is modified in any way — even one bit — decryption will fail and you will know the data is corrupted or has been tampered with. This makes AES-256-GCM significantly more secure than older modes like CBC, which encrypt but do not authenticate.

Encryption vs Hashing

Feature	Encryption	Hashing
Reversible	Yes (with the correct key)	No — one-way only
Needs a key/passphrase	Yes	No
Use case	Storing and transmitting secrets you need to read back	Verifying passwords and file integrity
Example algorithms	AES-256-GCM, ChaCha20-Poly1305	SHA-256, bcrypt, Argon2

When to Use This Tool

Encrypting notes or snippets — protect sensitive text (API keys, credentials, personal notes) before storing or sharing.
Learning about AES — understand how encryption and decryption work with a real implementation.
Quick client-side encryption — everything runs in your browser; nothing is sent to a server.

Important: For production systems, use a dedicated secrets manager (AWS Secrets Manager, HashiCorp Vault) rather than manual encryption tools. The strength of AES-256 is only as good as the passphrase you choose — use a long, random passphrase.

Encryption / Decryption

What Is AES Encryption?

How AES-256-GCM Works

Encryption vs Hashing

When to Use This Tool

Frequently Asked Questions