What is the AES file format?
An .aes file is encrypted using a 256-bit AES key. Decoding the file requires that the user provides a password. .aes is capable of encrypting any type of data - documents, images, archives, or executables. Encrypted files are not significantly larger than the input files; the format adds only around 130 bytes of header and integrity overhead. Encrypted files can be used to securely exchange information between parties, preventing third parties from accessing the file data. Typically an .aes-encrypted file has the suffix appended - for example, Document.doc becomes Document.doc.aes.
The .aes format is defined by the AES Crypt open specification (maintained by Packetizer, Inc.). The current format is version 3, which uses AES-256 in CBC mode with a unique random session key and initialization vector per file, plus an HMAC-SHA256 integrity tag that causes decryption to fail if the file has been tampered with. The file header begins with the three-byte ASCII signature AES followed by a version byte. Related formats include .gpg and .pgp for public-key encryption.
Encrypting files is one of the most secure means of sending information - the HTTPS protocol also uses AES encryption internally. Decrypting an encrypted file without the password is not impossible, but requires so much time and computing resources that it is not feasible in practice, making .aes a widely trusted choice. AES Crypt is available on Windows, macOS, Linux, Android, and iOS, and the format specification is publicly documented.
Security & safety
RISK: MEDIUMAES Crypt files are intentionally encrypted and cannot be inspected without the password - this could be used to conceal malware. If you receive an unexpected .aes file with a password in a separate message, treat it with caution (classic malware delivery evasion tactic to bypass email scanners). Legitimate use is straightforward secure file transfer. AES-256 encryption is cryptographically strong; brute-forcing a strong password is computationally infeasible with current hardware.
Format details
in a nutshell- Adobe After Effects Stabilizer Settings - Rare legacy file from Adobe After Effects warp stabilizer - unrelated to encryption; uses .aes extension coincidentally.
Programs that open AES files
Windows2 apps
AES Crypt
Open-source Install AES Crypt; right-click the .aes file → AES Decrypt, enter password. Or drag file onto AES Crypt window. 
7-Zip (cannot decrypt AES Crypt format)
Open-source 7-Zip's AES-256 is for ZIP/7z encryption - it cannot open AES Crypt .aes files. Do NOT use. 
macOS1 app
AES Crypt
Open-source Download AES Crypt for macOS; double-click the .aes file and enter password, or use command line: aescrypt -d file.aes 
Linux1 app
AES Crypt
Open-source sudo apt install aescrypt (Ubuntu/Debian) or install from aescrypt.com; then: aescrypt -d file.aes 
Android1 app
AES Crypt (Android)
Free Install AES Crypt from Google Play; select the .aes file and enter password. Technical details
deep spec| Format specification | AES Crypt open specification, publicly documented by Packetizer, Inc. |
| Magic signature | `AES` (hex `41 45 53`) at offset 0, followed by 1-byte version number |
| Format versions | v1 (legacy), v2 (SHA-256 KDF), v3 (current, strengthened KDF) |
| Encryption algorithm | AES-256 in CBC mode |
| Session key | Unique random 256-bit session key generated per file; encrypted with a key derived from the user password |
| Initialization vector | Unique 128-bit random IV per file; two encryptions of the same file produce different ciphertext |
| Integrity check | HMAC-SHA256 over the entire ciphertext; decryption fails if the file has been tampered |
| File size overhead | Source file size + approximately 130 bytes (header + HMAC footer) |
| Byte order | Big-endian (network byte order) for multi-byte header fields |
| Compression | None; the source file is encrypted without any prior compression step |
| Original filename | Not preserved inside the container - content type is opaque |
| Extension convention | Original extension retained and `.aes` appended (e.g., `report.pdf.aes`) |
| Platform support | Windows, macOS, Linux, Android, iOS |
| Released | AES Crypt v1.0, circa 2009; format specification v3 added circa 2015 |
| Latest version | AES Crypt Stream Format version 3 (current) |
| Open standard | Yes · royalty-free |
| Specification | www.aescrypt.com |
AES conversions
Community Q&A
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