Password Compare Tool
Compare two passwords: identical or not, Levenshtein distance, similarity, shared prefix/suffix and warnings like 'only the digits changed'.
A new password that differs from the old one by a single digit or character is guessed quickly by attackers who know the old one. Comparison happens locally in your browser.
Runs entirely in your browser. Your data is never uploaded.
What is Password Compare Tool?
Enter an old and a new password (or any two) to see whether they are identical and how similar they are. The tool measures the edit distance and warns about typical lazy changes such as changing only the year, the case or adding a character.
How to use Password Compare Tool
- Type the first password into Old / first password.
- Type the second into New / second password.
- Read whether they are identical and check Edit distance and Similarity.
- Review the warnings; if any appear, choose a completely new password.
Example
Winter2023! and Winter2024!
The passwords are different. Edit distance 1, similarity 90.9%. Only the digits differ (e.g. Winter2023 → Winter2024).
When to use Password Compare Tool
Use it when changing a password to make sure the new one is not a small variation of the old one, or to debug why two seemingly identical passwords do not match. Both passwords stay in your browser.
How Password Compare Tool works
Edit distance is the Levenshtein distance computed over Unicode code points (insertions, deletions and substitutions). Similarity = 1 − distance / length of the longer password. The tool also counts identical leading and trailing characters and checks whether the passwords differ only by case, digits, symbols, appended or prepended characters, reversal, Unicode normalization (NFC vs NFD) or surrounding spaces.
Common Use Cases
- Checking that a new password is not just the old one with 2025 instead of 2024
- Finding invisible differences like trailing spaces or Unicode forms
- Explaining password-history rules to users
- Testing similarity checks for a password-change form
FAQs
Why is a similar new password a problem?
Attackers who know an old password from a breach try small variations first; Winter2024! falls quickly if Winter2023! is known.
Why can two passwords look identical but not match?
They may differ by a trailing space or use different Unicode forms for accented letters (é as one character or e + combining accent).
Are the passwords stored?
No. The comparison runs only in your browser.