Random Password Generator
Generate a password or passphrase with a real entropy estimate - free, no signup.
What this tool does
Choose Characters for a traditional random password (with uppercase, lowercase, digits and symbols you control), or Passphrase for a Diceware-style word-based password that's easier to type and remember. Either way, you get an honest entropy estimate in bits - the actual number of yes/no decisions of randomness in your password - not just a vague 'strong/weak' color bar.
Generates a random character password with adjustable length and character sets (uppercase, lowercase, digits, symbols).
Generates a Diceware-style passphrase from random common words, easier to type and remember than a character password.
Calculates and shows the actual entropy in bits for whatever you generate, using the real character-set-size or word-list-size math.
Draws passphrase words from the same 150-word pool (50 nouns, 40 verbs, 40 adjectives, 20 adverbs) behind this site's random word generator, worth about 7.2 bits of entropy per word - noticeably less than a classic 7,776-word Diceware list's roughly 12.9 bits per word, so it takes more words here to reach the same strength.
Rejects and re-draws any crypto value that would fall outside a clean multiple of the character set (or word pool) size, rather than using a plain modulo that would subtly favour some characters or words over others.
How to use it
- Choose Characters or Passphrase mode.
- Adjust the length (or word count) and options.
- Copy your password, or generate a new one.
Why use this generator
People choose weak, predictable passwords, and a random one removes the guesswork. An entropy estimate shows how strong it really is.
Why we built it
We built the random password generator to give a real entropy figure in bits from the actual character set and length. Test an existing one with the password strength checker and encrypt notes with the text encryption tool.
Who this tool is for
- Anyone creating a new account password
- IT admins and developers
- People who want a passphrase
When to use it
- Creating a new account password.
- Making a passphrase you can type.
- Generating keys for development or Wi-Fi.
- Replacing a reused password.
What the entropy number actually means
A real calculation, not a marketing-style strength bar.
Entropy, measured in bits, is the actual mathematical measure of how many possible passwords could have been generated the same way you generated yours - a password with 60 bits of entropy could be any one of 2^60 possibilities, so guessing it by brute force would take, on average, half that many attempts. This tool calculates that number directly from your actual settings (character set size and length, or word list size and word count) rather than showing a vague red-to-green bar that doesn't tell you what it's actually measuring.
A passphrase of random words needs more characters to reach the same entropy as a shorter random-character password, but is usually far easier to type and remember correctly - which is why Diceware-style passphrases are a widely recommended alternative to character-soup passwords for anything you need to type by hand regularly.
How this passphrase mode compares to a classic Diceware list
Diceware-style, not the original word list - and the difference changes how many words you need.
This tool's passphrase mode draws from the same 150-word pool used by the random word generator elsewhere on this site - 50 nouns, 40 verbs, 40 adjectives and 20 adverbs combined into one list. That gives each word about 7.2 bits of entropy (log2 of 150). The original Diceware word list, by contrast, has exactly 7,776 words - chosen so a word can be picked by rolling five dice - giving roughly 12.9 bits per word, nearly double. The practical effect: this tool's default of 5 words comes to only about 36 bits of entropy, just barely past 'Weak' into 'Reasonable', where 5 words from a true Diceware list would land solidly in 'Strong' territory around 65 bits. Neither number is wrong - they're just different pools - but it means passphrase mode here needs noticeably more words than a classic Diceware recipe to reach the same strength.
| Target strength | Words needed here (~7.2 bits/word) | Words needed with a 7,776-word Diceware list (~12.9 bits/word) |
|---|---|---|
| ~50 bits (Reasonable) | 7 words | 4 words |
| ~60 bits (edge of Strong) | 9 words | 5 words |
| ~80 bits (Strong) | 12 words | 7 words |
What you give it, and what you get back
| Item | Details |
|---|---|
| Type | Character password or word passphrase. |
| Options | Length and character sets. |
| Output | The password with its strength in bits. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| A site rejects the password | It may restrict symbols or length. | Adjust the character sets. |
| Password is hard to remember | Random strings are. | Use a passphrase or a password manager. |
| Strength seems low | Length matters most. | Increase the length. |
Assumptions and limitations
- The entropy calculation assumes every character or word was chosen with equal, independent randomness, which is true for what this tool generates - it doesn't estimate the strength of a password you typed yourself, which usually has much less real randomness than it appears to.
- The passphrase word pool is a curated common-word list; a targeted attacker who knows the exact word list could search it specifically, though this doesn't meaningfully weaken the passphrase for typical use.
Frequently asked questions
How do I generate a secure password online for free?
Choose Characters or Passphrase mode, adjust the settings, and a new password appears instantly with its entropy shown in bits.
What does the entropy number in bits mean?
It's the actual number of equally-likely possibilities your password could have been - a password with 60 bits could be any one of 2^60 possible passwords, which is what an attacker would have to search through on average.
Should I use Characters or Passphrase mode?
Passphrase mode is usually easier to type and remember correctly for the same strength; Characters mode is more compact for systems with a maximum length limit.
How random is this really?
It uses the browser's cryptographically secure random number generator throughout, with a rejection-sampling technique that avoids the subtle bias a naive modulo operation can introduce.
Is my generated password uploaded anywhere?
No. Generation happens entirely in your browser - nothing is sent to a server, and closing the tab clears it.
How many words are in the passphrase word pool?
150 words total - the same combined noun, verb, adjective and adverb pools this site's random word generator uses. That's smaller than a classic 7,776-word Diceware list, so each word here is worth about 7.2 bits of entropy instead of about 12.9.
Is a 5-word passphrase strong enough?
With this tool's pool, 5 words comes to only about 36 bits of entropy - just past 'Weak' into 'Reasonable'. For something in the 'Strong' range (80 bits or more), use at least 12 words here, or switch to Characters mode with a longer length instead.
Further reading
Why "random" on a computer usually isn't, and when that matters — Most software random numbers come from a formula, not chance — deterministic and predictable if you know the start. Fine for games, risky for passwords.