Password Generator
Strong random passwords with optional prefix, suffix and character rules.
About this calculator
Reused and guessable passwords remain the most common break-in route. This generator creates passwords with a cryptographically secure random source on our server, with the options that matter: length up to 64 characters, symbols on or off (for systems that reject them), optional prefix/suffix for naming schemes, and a no-repeat mode. Nothing is stored or logged — each password exists only in your browser.
The formula
Worked example
A 16-character password with symbols has ~103 bits of entropy — brute-forcing it at a trillion guesses per second would take longer than the age of the universe. A 8-character letters-only password falls in hours.
Common mistakes
- Reusing one strong password everywhere — a single site breach then opens every account.
- Meeting complexity rules with predictable substitutions (P@ssw0rd1) that crackers try first.
- Storing generated passwords in a plain text file instead of a password manager.
Frequently asked questions
Assumptions & limitations
Entropy is computed on the random portion only — prefixes and suffixes add length but not randomness.
Sources & verification
- National Cyber Security Centre — password guidance — UK government guidance on password strength and management
- PHP random_int() — Passwords are generated server-side with a cryptographically secure random number generator and are never stored
All sources last accessed 24 July 2026.
Spotted an error or an out-of-date figure? Report it — corrections are prioritised over all other work (see our corrections policy).