Password Strength Checker
Estimate password strength from entropy and weak patterns.Security & PrivacyPassword Strength Checker
Estimate strength from entropy and known-weak patterns. The password never leaves this browser tab.
About this tool
Entropy from character-pool size, minus penalties for dictionary words, sequences and repeats. The password is never transmitted, logged or stored — the analysis happens in the tab.
How to use the Password Strength Checker tool
- Type the password. Nothing leaves the page; there is no network call.
- Read the verdict. A 0-4 score with the entropy estimate.
- Fix the warnings. Each weak pattern found is named.
Supported formats
Input
- Plain text or file input
Output
- Converted or analysed output
Inputs are validated before anything is processed. Invalid values and unsupported files are rejected with a clear error instead of failing silently.
Frequently asked questions
How is entropy computed?
Length times log2 of the character-pool size — the standard first estimate.
What patterns are penalised?
Common dictionary words, sequential runs and single-character repeats.
Is high entropy enough?
It is necessary, not sufficient: uniqueness versus leaked databases matters too and cannot be checked locally.
Privacy
Everything you enter stays in this browser tab. There is no upload endpoint for tool inputs, no account, and no server-side copy of your text or files. Results are produced locally and disappear when you close the page.
No account is required and no file is ever uploaded. See the privacy policy for details about analytics and the limited data this site stores.
Known limitations
- No breach-database lookups; no markov-model style estimation.
Related tools
Other free tools from the same collection.