🔐 Strong Password Generator
By ToolNimba Editorial Team · Updated 2026-06-19
, The strongest passwords are long and random, exactly what humans are worst at inventing. This generator builds passwords from a cryptographically-secure random source right in your browser, so the result is never sent anywhere or stored. Choose the length and which character types to include, check the live strength meter, and copy your new password with one click.
What is the Password Generator?
A password's real strength is measured in entropy, the number of equally-likely possibilities an attacker would have to search through to guess it. Entropy is counted in bits, and each bit doubles the work: a 40-bit password has twice as many combinations as a 39-bit one. For a random password, entropy is simply the length multiplied by the bits-per-character of the pool you draw from. That is why length beats complexity. Adding one more random character to a 94-symbol pool adds about 6.6 bits every time, whereas swapping a letter for a symbol in a short password barely moves the needle. A long passphrase of random words can out-muscle a short string of cryptic punctuation.
Every character here is chosen with the browser's built-in crypto.getRandomValues(), a cryptographically-secure pseudo-random number generator (CSPRNG). The generation happens entirely on your device, nothing is transmitted to a server, nothing is logged, and the password disappears from memory when you close the tab. This matters because a generator that sends candidate passwords over the network, or seeds itself from a predictable source like the clock, can undermine the very randomness it promises. A CSPRNG is designed so that seeing some output gives no useful clue about the rest.
The other half of password security is never reusing one. Large breaches leak billions of username-and-password pairs, and attackers replay those pairs against other sites in what is called credential stuffing. If your email password also unlocks your bank, a single leak from a forgotten forum can cascade across your accounts. A unique, high-entropy password per site contains the damage to one place, and a password manager makes storing dozens of them effortless.
When to use it
- Creating a fresh, high-entropy password when you sign up for a new account.
- Rotating a password that showed up in a breach notification or a "have I been pwned" alert.
- Generating a long Wi-Fi (WPA2/WPA3) key that is hard to guess but only typed once.
- Producing a unique password per site to store in a password manager, so no two logins share a secret.
How to use the Password Generator
- Set the length with the slider (12+ is recommended, 16+ for important accounts).
- Toggle uppercase, lowercase, numbers and symbols to set the character pool.
- Click generate, check the strength meter, then copy.
Formula & method
Worked examples
How many bits does a 16-character password from a 94-symbol pool carry? (94 = upper + lower + digits + common symbols.)
- bits per character = log₂(94) ≈ 6.55
- total entropy = 16 × 6.55 ≈ 105 bits
Result: ≈ 105 bits, comfortably in the "excellent" tier and infeasible to brute-force.
Compare an 8-character password to a 12-character one, both from the same 94-symbol pool, to see how length scales entropy.
- 8 chars: 8 × log₂(94) ≈ 8 × 6.55 ≈ 52 bits
- 12 chars: 12 × 6.55 ≈ 79 bits
- difference = 27 bits ≈ 2²⁷ ≈ 134 million times more combinations
Result: Adding 4 random characters multiplied the work by over 100 million, length is the cheapest way to buy strength.
Password-strength tiers by entropy (rough guidance for random passwords)
| Entropy (bits) | Rating | Guidance |
|---|---|---|
| Below 28 | Very weak | Trivial to crack; avoid entirely. |
| 28 – 35 | Weak | May survive casual guessing, not a determined attacker. |
| 36 – 59 | Reasonable | Okay for low-value logins; not for email or finance. |
| 60 – 127 | Strong | Suitable for important accounts. |
| 128 and above | Excellent | Far beyond any feasible brute-force attack. |
Approximate entropy by length and character pool (random passwords)
| Length | Lowercase only (26) | Letters + digits (62) | All types (94) |
|---|---|---|---|
| 8 chars | ≈ 38 bits | ≈ 48 bits | ≈ 52 bits |
| 12 chars | ≈ 56 bits | ≈ 71 bits | ≈ 79 bits |
| 16 chars | ≈ 75 bits | ≈ 95 bits | ≈ 105 bits |
| 20 chars | ≈ 94 bits | ≈ 119 bits | ≈ 131 bits |
Common mistakes to avoid
- Reusing the same password across sites. One breach then unlocks every account that shares it (credential stuffing). Use a unique password per site.
- Relying on predictable leetspeak substitutions. Swapping "a" for "@" or "o" for "0" in a dictionary word adds almost no entropy, cracking tools try those substitutions automatically.
- Choosing a password that is too short. Under about 12 characters, even a mixed-case-plus-symbols password sits in reach of modern hardware. Length is the biggest lever.
- Basing it on personal information. Names, birthdays, pet names and favourite teams are easy to find or guess and shrink the real search space dramatically.
Glossary
- Entropy
- A measure of unpredictability in bits; for a random password it equals length × log₂(pool size). Each extra bit doubles the guessing effort.
- Brute-force attack
- Trying every possible combination until the password is found. Higher entropy makes this take impractically long.
- CSPRNG / crypto.getRandomValues()
- A cryptographically-secure pseudo-random number generator. The browser API used here to pick each character so the output cannot be predicted.
- Password manager
- An app that generates, stores and autofills a unique strong password for every site, so you only remember one master password.
- Credential stuffing
- Replaying username/password pairs leaked from one breach against other sites, which only works when passwords are reused.
Frequently asked questions
What makes a password strong?
Strength comes down to entropy, how many possibilities an attacker must search. Length matters most: aim for at least 12–16 random characters. A larger character pool (uppercase, lowercase, numbers and symbols) raises the bits per character, but adding length is the single biggest gain.
How long should a password be?
Twelve characters is a sensible floor for everyday accounts, and 16 or more for important ones like email, banking and your password-manager master key. From a full 94-character pool, 16 characters is about 105 bits of entropy, comfortably infeasible to brute-force.
Are these generated passwords safe and private?
Yes. They are built with crypto.getRandomValues(), the browser’s cryptographically-secure generator, entirely on your device. Nothing is transmitted to a server or logged, so no one, including us, ever sees the password.
Should I reuse the same password on more than one site?
No. Reusing a password means a single breach can unlock many accounts through credential stuffing. Generate a unique password for every site and let a password manager remember them.
How am I supposed to remember strong passwords?
You are not meant to. Store each generated password in a reputable password manager, which autofills them and only asks you to remember one strong master password. For the handful you must type by hand, a long random passphrase of several words is easier to recall than cryptic symbols.
What is entropy in a password?
Entropy is a measure of unpredictability, counted in bits. For a random password it equals the length multiplied by log₂ of the character-pool size. Each additional bit doubles the number of guesses an attacker needs, so higher entropy means a much harder password to crack.