Text Similarity Checker

Free text similarity checker: compare two strings and see the Levenshtein edit distance plus a similarity percentage. Great for fuzzy matching, deduplication and spotting near-duplicates. Private, runs in your browser.

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Paste both strings, then press Compare.

How text similarity checker works

This checker measures how different two strings are using the Levenshtein distance: the minimum number of single-character edits (insert, delete or substitute) needed to turn one string into the other. "kitten" to "sitting" takes three edits, for example.

The similarity percentage is 100 minus the distance as a share of the longer string, so identical strings are 100% and completely different strings are 0%. A normalized distance between 0 and 1 is also reported for easy comparison.

Because the comparison runs entirely in your browser, you can paste any two strings, filenames or short records to spot near-duplicates for fuzzy matching or deduplication without uploading anything.

Frequently asked questions

What is Levenshtein distance?
It is the smallest number of single-character insertions, deletions or substitutions required to change one string into the other. Fewer edits means the strings are more similar.
How is the similarity percentage calculated?
Similarity = 100 × (1 - distance / maxLength), where maxLength is the length of the longer string. Identical strings are 100% similar; strings with no characters in common trend toward 0%.
Is the comparison case-sensitive?
Yes. "Cat" and "cat" differ by one substitution, so they are not 100% similar. Lowercase both strings first if you want a case-insensitive comparison.
How long can the strings be?
The dynamic-programming algorithm uses memory proportional to the length of the shorter string, so it handles typical sentences and short records instantly. Very large documents may take a moment but still run locally.

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