Analyze password entropy, crack time, and check against known data breaches. Your password never leaves the browser.
All password analysis is performed locally in your browser. The breach check uses k-anonymity: only the first 5 characters of your password's SHA-1 hash are sent to Have I Been Pwned. The full hash never leaves your device.
About this tool
Detailed password analysis: entropy, crack time and pattern detection. 100% local, free.
What Is the Password Strength Tester?
The Password Strength Tester is a free browser-based developer tool that handles password strength tester operations entirely on your device without any server round-trips. Built with standard web APIs and JavaScript, it processes your input locally — no code, data, or file content is ever uploaded to a remote server. The tool supports password analyzer standards and handles edge cases like Unicode characters, special encoding modes, and large inputs. Performance is optimized for files up to 10MB+ using streaming parsers where applicable. Unlike online alternatives that require accounts or impose usage limits, this tool is completely free with no caps.
Who Should Use This Tool?
Software developers use this tool daily for password strength tester tasks during coding, debugging, and deployment workflows. DevOps engineers rely on it for quick password analyzer conversions when configuring servers or CI/CD pipelines. QA testers validate password entropy outputs against expected values. Students learning web development use it as a reference tool to understand how encoding and formatting actually work. Technical writers format code examples for documentation. The tool is especially valuable in secure environments where corporate policy prohibits pasting code into external websites — everything stays local.
How to Use the Password Strength Tester
Paste or type your input into the text area — the tool processes it instantly with no submit button needed. For password strength tester operations, select your desired mode or options from the dropdown controls. The output panel shows results in real time with syntax highlighting where applicable. Use the copy button to transfer results to your clipboard. For batch operations, the tool handles multiple inputs separated by newlines. All processing happens in your browser's JavaScript engine — close the tab and your data is gone. Keyboard shortcuts (Ctrl+Enter) trigger the primary action for power users.
Frequently asked
How does it estimate password crack time?
It calculates entropy (bits of randomness) based on character set size and length, then estimates crack time against offline attacks: 100 billion guesses/second (GPU cluster with hashcat) versus 10,000 guesses/second (online throttled login). A 12-character mixed-case password with symbols has ~71 bits of entropy—roughly 34,000 years at 100B guesses/second.
What common weaknesses does it detect?
It flags dictionary words, keyboard patterns (qwerty, 1qaz2wsx), repeated characters, sequential numbers, and common substitutions (@ for a, 0 for o). It also checks against the top 100,000 breached passwords from HaveIBeenPwned datasets. "P@ssw0rd123" scores as weak despite meeting typical complexity rules.
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