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What is an alphanumeric password? | ExpressVPN Glossary

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Alphanumeric password

What is an alphanumeric password?

An alphanumeric password is one that contains both letters and numbers. Including more possible characters greatly expands the number of valid combinations. This can make alphanumeric passwords harder to guess than those containing only letters or only numbers.

In practice, passwords that include symbols (@, #, &, etc.) as well as letters and numbers are sometimes described as more "complex." Adding symbols can increase the search space, but real-world strength depends on how unpredictably they’re chosen.

Why alphanumeric passwords improve security

Alphanumeric passwords are much harder to guess Mathematics can illustrate how the size of the character set affects the number of possible 8-character combinations:

Numeric (0–9): 10⁸, or 100 million possible combinations.
Alphabetic (a–z, lowercase only): 268, or 208 billion possible combinations.
Alphabetic (A–Z, uppercase and lowercase): 528, or 53.5 trillion possible combinations.
Alphanumeric: 628, or 218 trillion possible combinations.

If policies also allow passwords to include 32 special characters, the range of possibilities jumps to 948, or roughly 6.1 quadrillion combinations.

Depending on how the login system limits guessing attempts (e.g., rate limiting or lockouts), an 8-character password with a large character set can be time-consuming to brute-force in an online attack. In offline attacks (after a password-hash breach), guessing can be much faster. Longer passwords increase the number of possible combinations dramatically

Numbers aside, strength comes mostly from length and unpredictability. Many policies now focus on longer passwords (or passphrases) and blocking common or breached passwords, rather than requiring specific character types.

Examples of alphanumeric passwords

The actual strength of alphanumeric passwords depends on factors like length, randomness, and predictability. Below are examples of alphanumeric passwords with increasing complexity:

Weak example: john1985
Stronger example: R@inC0de82
Even stronger example: ah@DcrEfs)k3TQCR

The first example is lacking, as the characters appear to have a clear meaning that could easily be guessed (a name and year).

The second is better, as it is longer, mixes upper- and lowercase letters, and introduces symbols. But it still contains real words that are simply masked with similar characters.

Created with a password generator, the last is both longer and truly random.

Security risks and vulnerabilities

Although alphanumeric passwords can be stronger, they aren’t inherently more secure. Added complexity can make them harder to remember, which may lead to unsafe habits. Practices to avoid include:

Storing passwords carelessly: Plaintext files or unprotected notes can expose credentials; written passwords can be risky if they’re easily seen, copied, lost, or stolen.
Following predictable patterns: Alphanumeric passwords may be vulnerable if they follow common patterns or use easy-to-guess personal details.
Reusing passwords: Reuse across accounts increases exposure if one site is breached (credential stuffing). Using a password manager helps keep passwords unique.
Keeping passwords short: Character-type requirements can push shorter passwords, which are more vulnerable. Length is a primary driver of strength.

Best practices for using strong alphanumeric passwords

Securing accounts involves more than just using alphanumeric passwords. Passwords should be long and hard to guess, avoiding predictable patterns and personal information that a stranger or acquaintance could guess.

Memorizing dozens of strong passwords is not feasible for most people. Rather than reusing logins (which can cause serious problems if one is compromised), the best solution is to use a password manager.

With such a tool, only one strong master password is needed to unlock the vault that stores all other passwords. Many password managers use strong encryption and a zero-knowledge security model, meaning vault data is encrypted in a way the provider can’t read.

Password managers also often include tools to generate strong passwords, flag reused credentials, and inform users if saved credentials appear in known breach data.

Finally, even with strong alphanumeric passwords, enabling multi-factor authentication (MFA) whenever possible adds protection if a password is compromised (though MFA strength varies by method).

FAQ

Is an alphanumeric password the same as a strong password?

No, an alphanumeric password can be weak if it’s too short, predictable, reused, or has been compromised. However, using letters and numbers allows more possible combinations than purely numeric or purely alphabetic passwords, so it can be stronger. The best way to secure accounts is to use long, unique passwords, along with other important practices.

Are symbols required for a secure password?

Not necessarily, but they can make passwords harder to guess. Some websites limit which special characters (or how many) are allowed in passwords. Incorporating symbols can significantly increase the number of potential combinations.

How long should an alphanumeric password be?

It depends on how secure the password must be. Eight characters is the common minimum required length on many websites and services. For sensitive accounts, 16 characters or more is often recommended. That said, bad habits (such as reusing passwords or predictable patterns) can still make otherwise strong passwords vulnerable.

Why are simple number sequences insecure?

Attackers and password-guessing tools try common patterns first. They attempt sequences like “12345,” “qwerty,” and “password” because they're still widely used and easy to guess. For these reasons, it's best to use long, unique alphanumeric passwords.

Can a password manager create alphanumeric passwords automatically?

Yes, some password managers come with the ability to generate secure passwords. This avoids having to manually create long, complex strings. These passwords can be difficult to remember, which is why password managers store them in a secure vault unlocked by a master password. In general, only a single master password is needed.