Password Generator

A password generator creates a random password for you instead of asking you to invent one yourself. That matters because people are predictable. We reuse favourite words, names, dates, and patterns, and attackers know those habits well. A generator has no habits. It picks each character at random, so the result is much harder to guess or crack.

This free password generator runs entirely in your browser. Nothing you generate is stored, sent to a server, or tracked. Choose a length, choose which characters to include, and click the button. You can also make up to ten passwords at once, which is handy when you are setting up several new accounts. For more everyday tools like this one, visit our Other Calculators hub.

Below, we explain how entropy measures strength, include a worked example and a comparison table, and show how to read your result.

What Is the Password Generator?

The Password Generator is a small tool that builds a random string of characters to use as a password. You control three things: how long the password is, which character sets it can use, and how many passwords to create at one time.

The character sets are lowercase letters (26 characters), uppercase letters (26 characters), digits (10 characters), and symbols (32 characters). Used together, they give a pool of 94 possible characters for every position in the password. The larger that pool, and the longer the password, the more possible combinations an attacker would have to try.

Unlike a password you invent, a generated password carries no personal meaning — no birthday, pet, or team. That lack of meaning is exactly what makes it strong.

How Does It Work? Entropy Explained

Strength is measured in bits of entropy. The formula is simple:

Entropy = length × log₂(charset size)

Here, length is the number of characters in the password. Charset size is the number of different characters that could appear in each position — for example, 26 for lowercase only, or 94 when all four sets are used. The log₂ part converts that choice into bits, so entropy tells you roughly how many yes-or-no guesses an attacker would need, on average, to work through the possibilities.

Every extra character adds the same amount of entropy. With all sets on, each character adds about 6.55 bits, so adding four characters adds about 26 bits. That is why length is so powerful: it grows strength steadily and predictably.

Randomness quality matters just as much as the maths. This tool uses crypto.getRandomValues, the secure random generator built into your browser, plus rejection sampling to avoid modulo bias. Random bytes are not simply divided and rounded, because that would make some characters slightly more likely than others. Instead, any byte outside a fair range is rejected and drawn again, so every character has an equal chance. The tool also guarantees at least one character from each set you selected, when the length allows it, then shuffles the result securely.

How to Use the Password Generator

1. Set the password length with the slider or the number box. Sixteen characters is a good default for most accounts.
2. Choose the character sets. Leave lowercase, uppercase, digits, and symbols on for the strongest result, unless a website forbids certain characters.
3. Choose how many passwords you want, from 1 to 10.
4. Check the entropy display and the strength label. Aim for Strong or Excellent for important accounts.
5. Click Generate Password.
6. Click Copy next to the password you want, paste it into the sign-up or password-change form, and save it in a password manager.

If you enjoy tools that pick things fairly at random, try our Random Name Picker as well.

Password Generator Example

Suppose you choose a length of 16 and turn on all four sets. The pool is 26 + 26 + 10 + 32 = 94 characters.

Entropy = 16 × log₂(94) = 16 × 6.5546 ≈ 104.9 bits — Excellent, and very strong for normal use.

Compare 8 characters, lowercase only: Entropy = 8 × log₂(26) = 8 × 4.700 ≈ 37.6 bits — Weak. A longer password and a larger pool both raise entropy a lot.

The table below shows entropy for common lengths and pools. Alphanumeric means lowercase, uppercase, and digits together (62 characters).

Length	Lowercase only (26)	Alphanumeric (62)	All sets (94)
8	37.6 bits	47.6 bits	52.4 bits
12	56.4 bits	71.5 bits	78.7 bits
16	75.2 bits	95.3 bits	104.9 bits
20	94.0 bits	119.1 bits	131.1 bits

Notice that a 20-character lowercase-only password beats a 12-character password using all sets — length does heavy work. For other calculations, our Scientific Calculator handles logarithms.

Important Points and Assumptions

• Use a unique password for every account. If one site leaks, the others stay safe.
• Save generated passwords in a trusted password manager. A strong password you cannot remember is only useful if it is stored safely.
• Generator quality depends on your device’s cryptographic random number generator, which modern browsers provide. Keep your browser up to date.
• Entropy assumes every character is chosen randomly and equally. It does not apply to passwords invented from words or patterns.
• Some websites limit length or forbid some symbols. If a site rejects a password, reduce the length or turn symbols off and generate again.

Common Mistakes

• Reusing the same generated password everywhere. Generating is fast, so make a fresh one for each account.
• Choosing a very short length. An 8-character password is weak even with all sets on. Prefer 16 or more.
• Writing passwords on paper left near the computer. Use a password manager instead.
• Shortening the password by hand. Cutting characters removes entropy. If a site sets a maximum, generate at that maximum.
• Sharing a password by email or message. Anyone who needs access should have their own account and password.

How to Interpret Your Result

The tool shows entropy in bits and a plain strength label. Use these bands:

• Under 40 bits — Weak: too easy to guess or crack. Make it longer.
• 40 to 59 bits — Fair: acceptable only for low-value accounts. Longer is still better.
• 60 to 79 bits — Strong: a solid choice for most accounts.
• 80 bits or more — Excellent: a very strong password, suitable for email, banking, and other important accounts.

Your email account deserves an Excellent password, because it can reset almost every other account. The same applies to your password manager’s master password.

Frequently Asked Questions

Is this password generator free?

Yes. It is free to use, needs no sign-up, and you can generate as many passwords as you like.

Are my passwords sent to a server?

No. Passwords are generated locally in your browser using its secure random generator. Nothing is sent, stored, or logged by this tool.

What length should I choose?

Choose at least 16 characters for important accounts. If a website allows more and your password manager stores it for you, 20 characters is even better.

Why include symbols?

Symbols increase the pool from 62 to 94 characters, which raises entropy for the same length. If a website forbids symbols, turn them off and add a few extra characters instead.

Can I use one generated password for several sites?

No. Always generate a unique password for each account, so a leak at one site cannot unlock the others.

What if I forget a generated password?

That is normal — generated passwords are not meant to be memorised, except for a master password. Store the rest in a password manager, and use the site’s password reset process if you lose access.

References

National Institute of Standards and Technology (NIST), SP 800-63B: Digital Identity Guidelines — Authentication and Lifecycle Management, covering memorized secrets and password length: https://pages.nist.gov/800-63-3/sp800-63b.html