Password Strength Checker
Local entropy and checklist-based password strength check.
Estimated entropy: 56.9 bits · charset size 36
- At least 8 characters
- At least 12 characters
- Contains a lowercase letter
- Contains an uppercase letter
- Contains a number
- Contains a symbol
- No 3+ repeated characters in a row
- No obvious sequences (abcd, 1234)
- Not a commonly leaked password
- This password appears on common breach/weak-password lists.
- Use at least 12 characters for meaningfully stronger passwords.
Password Strength Checker analyzes a password entirely in your browser, estimating entropy, checking a security checklist, and flagging common weak patterns. Nothing is uploaded or stored, so it is safe to test real password candidates before committing to them.
How it works
As you type, a local heuristic inspects password length and character classes (lowercase, uppercase, numbers, symbols) to estimate entropy in bits, checks for known weak passwords, repeated characters, and simple sequences, then maps the result to a five-level strength score with a checklist you can act on.
Benefits
- Fully local analysis—your password is never sent anywhere
- Entropy estimate plus an actionable checklist
- Flags common weak passwords, repeats, and sequences
- History disabled entirely since the input is a secret
Use cases
- Sanity-check a new password before saving it in a password manager
- Teach password hygiene with a visible, local scoring breakdown
- Audit example passwords used in documentation or onboarding guides
- Compare candidate passphrases for a shared or admin account
Best practices
- Prefer a unique, generated password stored in a password manager over a memorized one
- Use at least 12–16 characters with a mix of character classes
- Avoid dictionary words, keyboard sequences, and personal information
- Treat any strength meter as a hint, not a guarantee of real-world security
Common mistakes
- Assuming length alone guarantees strength while ignoring repeats and sequences
- Reusing a password that scores well here across multiple accounts
- Typing a real production password into any third-party tool, including this one, on an untrusted device
- Treating a 'strong' local score as proof the password has not appeared in a breach
Privacy
Analysis runs entirely client-side with plain JavaScript—no network request is made and no password is logged. Because the input is itself sensitive, on-device history is disabled entirely for this tool rather than offered as opt-in.
Frequently asked questions
- Does Password Strength Checker store or upload my password?
- No. The password you type is analyzed locally in your browser using a JavaScript heuristic and is never transmitted, logged, or stored. History is disabled entirely for this tool.
- How is the strength score calculated?
- The tool estimates entropy from length and the character classes used (lowercase, uppercase, numbers, symbols), then checks for common weak passwords, repeated characters, and simple sequences to produce a five-level score.
- Is this a substitute for a password manager?
- No. This tool only estimates strength locally—it does not generate, store, or sync passwords. Use a dedicated password manager to create and store unique passwords per account.
- Why did a long password still score poorly?
- Length alone is not enough. Repeated characters, keyboard sequences (like "abcd" or "1234"), and known leaked passwords lower the score even when the password is long.
- What does entropy in bits mean here?
- Entropy estimates how many attempts, on average, a brute-force attacker would need. It is calculated from password length and character variety and is an estimate, not a guarantee.
- Should I trust any strength meter completely?
- No single client-side heuristic can fully predict real-world crackability. Use this as a quick sanity check alongside a password manager and, where available, breach-database checks.
- Why is history disabled for this tool?
- Because the input is itself a password (a secret), history storage is disabled entirely rather than opt-in, so nothing is ever written to LocalStorage for this tool.
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