AES Encryption / Decryption Tool

Encrypt and decrypt text free online using real AES-256-GCM via the browser's Web Crypto API. Industry-standard encryption, not a toy cipher, all client-side.

Passphrase Text to Encrypt

Real AES-256-GCM via Web Crypto API -- everything stays in your browser.

How to Use This Tool

Choose encrypt or decryptSelect the operation you want to perform

Enter your passphraseThis derives the actual encryption key via PBKDF2

Encrypt or decrypt your textGet a Base64-encoded ciphertext, or readable plaintext back

AES Encryption / Decryption Tool is a free online tool that works entirely in your browser — no signup, no data uploaded, no limits.

Real Browser-Native Cryptography, Not a JavaScript Reimplementation

Many online "encryption tools" implement their own simplified cipher in JavaScript, which is risky because cryptographic algorithms are notoriously easy to implement incorrectly in subtle ways that undermine security. This tool instead calls the Web Crypto API's SubtleCrypto interface directly -- the same audited, standardized cryptographic engine browsers use for HTTPS connections and other security-critical operations.

AES-256-GCM is the specific algorithm and mode used: AES-256 for the encryption strength, GCM for combined encryption and tamper detection. This combination is widely considered the current standard for symmetric encryption in modern applications.

Why a Passphrase Is Not Used Directly as the Key

A human-chosen passphrase, even a good one, has far less entropy than a properly random 256-bit key. PBKDF2 with 100,000 iterations and a random salt deliberately makes deriving the actual encryption key from the passphrase slow and resistant to brute-force guessing, closing the gap between human-memorable input and cryptographic-grade key strength.

Why GCM Mode Specifically

Older AES modes like ECB have well-documented weaknesses (identical plaintext blocks produce identical ciphertext blocks, leaking patterns). CBC mode fixes that but provides no built-in way to detect tampering. GCM mode provides both strong encryption and an authentication tag that detects if the ciphertext was modified after encryption -- exactly the properties a general-purpose encryption tool should default to.

Frequently Asked Questions

This is real AES-256-GCM encryption performed by the browser's native Web Crypto API (SubtleCrypto), the same cryptographic engine browsers use for HTTPS and other security features. It is not a simplified JavaScript reimplementation -- it calls the actual, audited cryptographic primitives built into the browser.

GCM (Galois/Counter Mode) provides both encryption and authentication in one operation. It detects if encrypted data has been tampered with after encryption, which basic AES modes like ECB or CBC do not provide on their own. This is why GCM is the recommended mode for most modern applications.

Your passphrase is run through PBKDF2 (Password-Based Key Derivation Function 2) with a random salt and 100,000 iterations, which is the standard, recommended approach for turning a human-memorable passphrase into a cryptographically strong key, rather than using the passphrase directly as a weak key.

If you have the exact key derivation parameters (salt, iteration count) and IV used originally, yes -- this tool implements the standard, so output is interoperable with other correct AES-GCM implementations as long as the parameters match.

No. All encryption and decryption happens locally using the Web Crypto API running in your browser. Nothing is transmitted anywhere, which is important since you would not want sensitive data leaving your device during encryption.