What AES encryption online should (and should not) do#
AES (Advanced Encryption Standard) is the block cipher almost every modern system uses to keep data confidential. An AES encryption online tool is useful when you need to encrypt text AES 256 for a quick test, a demo, or a local workflow — but only if cryptography runs in your browser. This page is an AES encryption and decryption workspace built on the Web Crypto API: plaintext, passphrases, and raw keys are processed locally and are never uploaded.
That client-side boundary matters for encrypt text AES 256 online use cases. A server-side “free encryptor” that accepts your secret over HTTP is asking you to trust an unknown operator with the very data you wanted to protect. Prefer tools that state clearly that work stays on-device, and treat even a good browser tool as a convenience layer — not a full key-management product.
AES-256 vs AES-128, and what AES-256-GCM actually is#
AES-128 and AES-256 describe the key length (128 or 256 bits). Both are secure when used correctly; AES-256 is the common default in new designs and is what people mean by AES 256 encrypt decrypt online. The larger key raises the brute-force cost further, which is why this tool defaults to 256-bit keys.
What is AES-256-GCM? It is AES with a 256-bit key in Galois/Counter Mode. GCM encrypts and also authenticates: if someone tampers with the ciphertext or you use the wrong key, decryption fails instead of returning silent garbage. That is why AES 256 GCM online / AES GCM encryption online tool workflows prefer GCM over older modes for new work. Is AES-256-GCM secure? Yes, when IVs are unique per key, implementations are constant-time and vetted (as in Web Crypto), and keys stay secret. It is widely standardized and used in TLS 1.3 and many storage systems.
GCM vs CBC, keys, and CryptoJS compatibility#
AES-CBC only provides confidentiality (with PKCS#7 padding in Web Crypto). It does not authenticate. A wrong key may yield nonsense plaintext rather than a hard failure, and CBC needs careful IV handling. Prefer AES-GCM unless you must interoperate with a CBC-only peer. This tool still offers CBC for those cases.
An AES encryption key is raw key material — 16 bytes for AES-128 or 32 bytes for AES-256 — usually shown as hex or Base64. The built-in AES encryption key generator fills a cryptographically random hex key via crypto.getRandomValues. A passphrase is not the AES key itself: this tool runs PBKDF2-HMAC-SHA-256 (210,000 iterations) with a random salt stored in the JSON package so the same passphrase can unlock the ciphertext later.
People searching cryptojs aes often expect OpenSSL-compatible ciphertext from the CryptoJS library. This tool does not use CryptoJS. It uses the browser’s Web Crypto API. The ideas (AES, GCM/CBC, passphrases) overlap, but ciphertext encodings, KDF parameters, and OpenSSL “Salted__” blobs are not interchangeable. Decrypt CryptoJS output with CryptoJS (or a matching OpenSSL pipeline); use this package format with this tool.
Output format and safe habits#
On encrypt, a fresh IV is generated (12 bytes for GCM, 16 for CBC), shown for inspection, and embedded in a JSON package: alg, ks, iv, ct, plus salt and iter when a passphrase was used. You can also paste compact iv:ct or salt:iv:ct (Base64) on decrypt if you set algorithm and key size in the UI. Never reuse an IV with the same key in GCM. Store raw keys like passwords. For real production systems, use a proper KMS or sealed secrets — this page is for transparent, local AES encryption examples and day-to-day encrypt/decrypt checks.