---
title: "What Is AES-256 Encryption? A Plain-English Explanation"
description: "AES-256 is a widely used encryption standard with a 256-bit key. What the numbers mean, AES-128 vs AES-256, and why the key matters more than the cipher."
url: https://www.vaultforyou.app/glossary/aes-256
lang: en
published: 2026-10-31
updated: 2026-10-31
author: "VaultForYou Editorial Team"
publisher: VaultForYou
---

# What is AES-256?

Published 2026-10-31 - Updated 2026-10-31 - By VaultForYou Editorial Team

## Quick answer

AES-256 is the Advanced Encryption Standard used with a 256-bit key. AES is a symmetric cipher, meaning the same key encrypts and decrypts, and it is one of the most widely used ways to encrypt files, disks and network traffic.

- **Type:** Symmetric block cipher.
- **Key sizes:** 128, 192 or 256 bits.
- **Weak point:** How the key is stored, not the cipher.

The number is the key length. Both AES-128 and AES-256 are considered strong; AES-256 has a longer key and a larger safety margin. In practice, data protected by AES is lost to attackers through stolen passwords, keys or unlocked devices, not by breaking the cipher.

When an app advertises a cipher, the questions that matter more are where the key is kept and who else can get it.

## Frequently asked questions

### What does 256 mean in AES-256?

It is the length of the encryption key in bits. AES can use 128-, 192- or 256-bit keys. A longer key means far more possible keys to guess. Both AES-128 and AES-256 are considered secure for everyday use.

### Is AES-256 unbreakable?

No practical attack breaks the cipher itself, but encrypted data is still exposed if the key or password is stolen, weak or stored somewhere others can reach. How the key is protected matters more than the number in the name.

## Guides that use this term

- [What is zero-knowledge encryption, and how can you tell if an app uses it?](https://www.vaultforyou.app/blog/zero-knowledge-encryption)
- [Is iCloud encrypted? Standard vs. Advanced Data Protection](https://www.vaultforyou.app/blog/is-icloud-encrypted)

## Related terms

- [End-to-end encryption](https://www.vaultforyou.app/glossary/end-to-end-encryption)
- [iOS Keychain](https://www.vaultforyou.app/glossary/keychain)

## Browse

- [All glossary terms](https://www.vaultforyou.app/glossary)

---

Our guides are written and fact-checked by the VaultForYou team against Apple's own documentation. We make VaultForYou, a private vault app for iPhone. Download on the App Store: https://apps.apple.com/app/vaultforyou/id0000000000