Free Tool

OSA Damerau-Levenshtein Distance

Calculate edit distance allowing insertions, deletions, substitutions, and transpositions — catches swapped adjacent characters like "teh" → "the".

Tilores uses OSA Damerau-Levenshtein in production — so you can automate matching with rules you configure.

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Try it yourself

String A

String B

Edit Distance

Match

How it works

The Optimal String Alignment (OSA) variant of Damerau-Levenshtein distance extends standard Levenshtein by adding transposition as a fourth allowed operation. This means swapping two adjacent characters counts as a single edit rather than two. "teh" and "the" have an OSA distance of 1 (one transposition), but a Levenshtein distance of 2. The OSA variant has one restriction: it does not allow a substring to be edited more than once, which makes it slightly simpler but different from the true Damerau-Levenshtein in rare edge cases.

Use cases in entity resolution

Typo correction for transposed characters

Keyboard adjacency error detection

OCR error correction

Fast approximate string matching

Related tools

Levenshtein Distance

Calculate the minimum number of single-character edits (insertions, deletions, substitutions) needed to transform one string into another.

Damerau-Levenshtein Distance

The true Damerau-Levenshtein distance — edit distance with unrestricted transpositions, the most accurate metric for real-world typing errors.

LCS Edit Distance

Edit distance based on the Longest Common Subsequence — counts only insertions and deletions, making it useful for comparing sequences where order matters.

Don't implement this yourself

Tilores Studio runs the full matching engine — this algorithm plus configurable rules and real-time entity resolution — locally on your machine. Free, no account, no cloud. Load your own data and see it working in minutes.

Download Tilores Studio