AES Encrypt / Decrypt — Free Online Tool AES encrypt/decrypt text online: 128/192/256-bit keys, CBC/GCM/ECB modes. Secure AES encryption with IV, PKCS7 padding. Online AES cipher tool.
Use this free online AES Encrypt / Decrypt directly in your browser. No signup required, no data leaves your device. Part of Utilier — a collection of 133+ developer utilities.
What is AES Encryption/Decryption (128, 192, 256-bit, CBC, GCM Modes)? AES (Advanced Encryption Standard) encryption tool encrypts and decrypts data using symmetric key cipher with 128/192/256-bit key lengths, multiple modes (CBC, GCM, ECB, CTR), initialization vector (IV) for randomness, and PKCS7 padding for block alignment.
Key sizes: AES-128 (128-bit, 16 bytes), AES-192 (192-bit, 24 bytes), AES-256 (256-bit, 32 bytes). Longer = more secure, slightly slower.Modes: CBC (Cipher Block Chaining, needs IV), GCM (Galois/Counter Mode, authenticated encryption), ECB (insecure, don't use), CTR (Counter mode).IV (Initialization Vector): Random 16-byte value. Required for CBC, GCM. Makes same plaintext encrypt to different ciphertext. Must be unique per encryption.Padding: PKCS7 padding for CBC/ECB (blocks must be 16 bytes). GCM/CTR no padding (stream cipher modes).Why use aes encryption? Industry-standard encryption. Secure data at rest and in transit.
Military-grade: AES-256 used by US government for classified data. Unbreakable with current technology.Fast: Hardware-accelerated on modern CPUs (AES-NI instructions). Encrypts GB/sec.Standard: Widely supported: databases (TLS), files, messaging. Interoperable implementations.When to use aes encryption Use for encrypting sensitive data.
Encrypting database fields (passwords, SSN, credit cards). File encryption (documents, backups). Secure messaging (end-to-end encryption). API data protection (encrypt payloads). Password managers (vault encryption). How to use aes encryption Enter text and key, encrypt or decrypt.
Enter plaintext: Type sensitive data to encrypt: 'Secret message'.Set key: AES-256: 32-character key (256 bits / 8 = 32 bytes). Random key recommended.Choose mode: GCM (best: authenticated encryption), CBC (common), CTR (stream cipher). Avoid ECB (insecure).Encrypt: Click Encrypt. Generates IV, encrypts, outputs ciphertext (base64) + IV.Decrypt: Enter ciphertext, IV, same key. Click Decrypt. Outputs original plaintext.Key features Multiple key sizes: AES-128, AES-192, AES-256. Longer key = more secure.Secure modes: GCM (authenticated), CBC (standard), CTR (stream). ECB avoided (insecure).Random IV: Auto-generates unique IV per encryption. Prevents pattern detection.Base64 output: Ciphertext encoded in base64 for text transmission. Decode to decrypt.Common use cases Encrypt password: User password before storing: AES-256-GCM encrypt with master key. Store ciphertext + IV in database.File encryption: Document: read file, encrypt content, save as encrypted. Decrypt when needed with same key.API payload: Encrypt sensitive API data: AES-256-GCM, send ciphertext + IV. Recipient decrypts with shared key.Examples AES encryption examples.
Encrypt text Plaintext: 'Secret message'
Key (32 chars): 'my32characterpasswordkey12345678'Ciphertext: U2FsdGVkX1...(base64)
IV: a1b2c3d4e5f6...(hex)AES-256-GCM encrypted. IV randomly generated.
Technical reference AES encryption specifications.
Algorithm Rijndael cipher (AES standard). Block size: 128 bits (16 bytes). Rounds: 10 (AES-128), 12 (AES-192), 14 (AES-256). Modes GCM: authenticated encryption (detects tampering). CBC: needs IV, secure with random IV. ECB: no IV, insecure (patterns visible). CTR: stream cipher. IV 16 bytes (128 bits). Must be random and unique per encryption. Not secret (transmitted with ciphertext). Reusing IV = security breach. Padding PKCS7: adds 1-16 bytes to make block size multiple of 16. CBC/ECB need padding. GCM/CTR: no padding (stream modes). Common mistakes to avoid Using ECB mode (reveals patterns) Why it happens: ECB encrypts each block independently. Same plaintext block → same ciphertext. Patterns visible (penguin image example).
How to avoid it: Use CBC or GCM. Requires IV but secure. GCM best (authenticated encryption).
Reusing IV (breaks security) Why it happens: Same key + IV = predictable ciphertext. Attacker can XOR ciphertexts to find plaintext XOR.
How to avoid it: Generate random IV for every encryption. Store IV with ciphertext (not secret).
Frequently asked questions AES-128 vs AES-256: which is better? AES-256 more secure (larger key space). AES-128 still unbreakable with current tech. AES-256 for top secret data, AES-128 sufficient for most uses.
Is IV secret? No. IV can be public (transmitted with ciphertext). Must be random and unique per encryption, but not secret like the key.
Privacy and availability Runs entirely in your browser — zero server processing No signup or account required Works offline once loaded Fast, lightweight, no external dependencies Available as a browser extension for Chrome and Firefox Tags CI/CD Networking Security Related tools RSA Encrypt / Decrypt — Generate an RSA keypair and encrypt/decrypt short messages with RSA-OAEP (SHA-256). Keys are PEM. Best for small payloads (≈190 bytes at 2048-bit).Hash Generator — Compute MD5, SHA-1, SHA-256, SHA-384, SHA-512, and CRC-16 digests of text.Password Generator — Generate strong random passwords with configurable character sets.Base64 / Base32 / Base58 / Base85 Encoder — Encode and decode text using Base64, Base32, Base58, Base85, or ASCII85.BCrypt Generator — Hash a password with bcrypt (Blowfish-based, salted) at a configurable cost, or verify a password against an existing bcrypt hash.All developer tools JSON Beautifier & Validator — Format, minify and validate JSON. 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