What makes a password strong?
Length beats complexity. Each extra character multiplies the guesses an attacker must try. A 16-character password drawn from all character types has about 9516 possibilities — at 10 billion guesses per second that is still millions of years of brute force. A short 8-character password, even with symbols, falls in hours.
But brute force is not the real threat. Most breaches come from leaked password lists, dictionary attacks and credential stuffing — reusing one password across sites. A "strong" password that you reuse everywhere is weaker in practice than a unique medium password per site.
How to build passwords you can actually use
- Use a password manager. It generates and remembers long random passwords; you memorize one master passphrase.
- Prefer passphrases. Four or five random words ("correct horse battery staple") are long, memorable and hard to guess.
- Never reuse. One breach should never unlock your email, bank and social accounts together.
- Turn on two-factor authentication everywhere important — it blocks most attacks even if a password leaks.
Reading the crack-time estimate
The estimate assumes 10 billion guesses per second against the full character space. Real attackers are often faster with smart wordlists, and slower against truly random strings. Treat it as an order-of-magnitude guide, not a guarantee.