---
title: "String similarity: Levenshtein, Jaro-Winkler distance and Soundex/Metaphone phonetic keys"
method: GET
path: "/v1/text/similarity"
tags: ["deterministic", "no-api-key", "text", "similarity", "phonetic"]
---

# String similarity: Levenshtein, Jaro-Winkler distance and Soundex/Metaphone phonetic keys

`GET /v1/text/similarity`

## Request

- Base URL: `https://api.duoleads.com`
- URL: `https://api.duoleads.com/v1/text/similarity`
- Auth: none declared

String similarity: compare two strings and return every standard measure in one call: Levenshtein and Damerau-Levenshtein edit distance, normalised similarity, Jaro and Jaro-Winkler, longest common subsequence, Dice coefficient on character bigrams, and the Soundex, Metaphone and NYSIIS phonetic keys of each string. Optional case folding, accent folding and whitespace normalisation before comparison.

**Output (`data`):** levenshtein, damerau_levenshtein, normalised_similarity (0-1), jaro, jaro_winkler, lcs_length, dice, phonetic {a: {soundex, metaphone, nysiis}, b: {...}} (Soundex, Metaphone and NYSIIS are computed exactly as the jellyfish library does, on the folded string; with only=soundex|metaphone|nysiis just that key), equal_after_fold, folded {a, b}.

Deterministic: identical input returns identical output, so the response is served with `Cache-Control: private, max-age=31536000, immutable` (the paying client may cache it indefinitely; shared caches must not, because the response is paid).

Price: $0.05 USDC per call (x402, Base). Route contract version 1.0.0. Docs: https://api.duoleads.com/docs#text-similarity

## Query parameters

- `a` string, required
- `b` string, required
- `fold` string
- `only` string

## Response `200`

Paid and settled. `data` is route-specific; a route that judges its input returns 200 with `data.valid: false` for a bad value.

- object
  - `ok` unknown, required
  - `route` '/v1/text/similarity', required
  - `version` '1.0.0', required
  - `data` object, required: levenshtein, damerau_levenshtein, normalised_similarity (0-1), jaro, jaro_winkler, lcs_length, dice, phonetic {a: {soundex, metaphone, nysiis}, b: {...}} (Soundex, Metaphone and NYSIIS are computed exactly as the jellyfish library does, on the folded string; with only=soundex|metaphone|nysiis just that key), equal_after_fold, folded {a, b}.
    - `levenshtein` number
    - `damerau_levenshtein` number
    - `normalised_similarity` number
    - `jaro` number
    - `jaro_winkler` number
    - `lcs_length` integer
    - `dice` number
    - `phonetic` object
      - `a` object, required
        - `soundex` string
        - `metaphone` string
        - `nysiis` string
      - `b` object, required
        - `soundex` string
        - `metaphone` string
        - `nysiis` string
    - `equal_after_fold` boolean, required
    - `folded` object, required
      - `a` string, required
      - `b` string, required
  - `meta` Meta, required
    - `disclaimer` string, required: Legal short disclaimer, identical on every response.
    - `request_id` string, required: ULID.
    - `computed_at` string, date-time, required: RFC 3339 UTC with milliseconds.
    - `price_usd` string, required: Decimal string, "0.05".
    - `deterministic` boolean, required
    - `sources` object[]: Present only on routes that read a vendored dataset: the exact edition that answered.
      - `id` string, required
      - `version` string, required
      - `published` string, required
      - `attribution` string
      - `licence` string

## Other responses

- `400`: MISSING_PARAM, INVALID_PARAM or UNSUPPORTED_VALUE. Not charged: validation runs before the paywall.
- `402`: Payment required. No valid PAYMENT-SIGNATURE was supplied: read the base64 PAYMENT-REQUIRED header (or this body) for the price ($0.05 = 50000 atomic USDC on eip155:8453), sign an EIP-3009 authorization and retry. Also returned when settlement is declined (PAYMENT_FAILED). Nothing is charged on a 402.
- `404`: NOT_FOUND: unknown path. Not charged.
- `405`: METHOD_NOT_ALLOWED: only GET and HEAD are served. Not charged.
- `413`: INPUT_TOO_LARGE: a parameter exceeded its documented maximum length. Not charged.
- `500`: INTERNAL: a server bug. Not charged.

---

[API](https://skmtc.dev/duoleads/apis/duo-data-utilities-iban-isin-vat-tax-id-barcode-timezone-geo.md) · [All operations](https://skmtc.dev/duoleads/apis/duo-data-utilities-iban-isin-vat-tax-id-barcode-timezone-geo/llms.txt) · [OpenAPI document](https://skmtc.dev/duoleads/apis/duo-data-utilities-iban-isin-vat-tax-id-barcode-timezone-geo/revisions/18790d59615e?raw)