--- layout: default title: Fuzzy parent: Term-level queries grand_parent: Query DSL nav_order: 20 --- # Fuzzy query A fuzzy query searches for documents containing terms that are similar to the search term within the maximum allowed [Levenshtein distance](https://en.wikipedia.org/wiki/Levenshtein_distance). The Levenshtein distance measures the number of one-character changes needed to change one term to another term. These changes include: - Replacements: **c**at to **b**at - Insertions: cat to cat**s** - Deletions: **c**at to at - Transpositions: **ca**t to **ac**t A fuzzy query creates a list of all possible expansions of the search term that fall within the Levenshtein distance. You can specify the maximum number of such expansions in the `max_expansions` field. Then it searches for documents that match any of the expansions. The following example query searches for the speaker `HALET` (misspelled `HAMLET`). The maximum edit distance is not specified, so the default `AUTO` edit distance is used: ```json GET shakespeare/_search { "query": { "fuzzy": { "speaker": { "value": "HALET" } } } } ``` {% include copy-curl.html %} The response contains all documents in which `HAMLET` is the speaker. The following example query searches for the word `HALET` with advanced parameters: ```json GET shakespeare/_search { "query": { "fuzzy": { "speaker": { "value": "HALET", "fuzziness": "2", "max_expansions": 40, "prefix_length": 0, "transpositions": true, "rewrite": "constant_score" } } } } ``` {% include copy-curl.html %} ## Parameters The query accepts the name of the field (`<field>`) as a top-level parameter: ```json GET _search { "query": { "fuzzy": { "<field>": { "value": "sample", ... } } } } ``` {% include copy-curl.html %} The `<field>` accepts the following parameters. All parameters except `value` are optional. Parameter | Data type | Description :--- | :--- | :--- `value` | String | The term to search for in the field specified in `<field>`. `fuzziness` | `AUTO`, `0`, or a positive integer | The number of character edits (insert, delete, substitute) needed to change one word to another when determining whether a term matched a value. For example, the distance between `wined` and `wind` is 1. The default, `AUTO`, chooses a value based on the length of each term and is a good choice for most use cases. `max_expansions` | Positive integer | The maximum number of terms to which the query can expand. Fuzzy queries “expand to” a number of matching terms that are within the distance specified in `fuzziness`. Then OpenSearch tries to match those terms. Default is `50`. `prefix_length` | Non-negative integer | The number of leading characters that are not considered in fuzziness. Default is `0`. `rewrite` | String | Determines how OpenSearch rewrites and scores multi-term queries. Valid values are `constant_score`, `scoring_boolean`, `constant_score_boolean`, `top_terms_N`, `top_terms_boost_N`, and `top_terms_blended_freqs_N`. Default is `constant_score`. `transpositions` | Boolean | Specifies whether to allow transpositions of two adjacent characters (`ab` to `ba`) as edits. Default is `true`. Specifying a large value in `max_expansions` can lead to poor performance, especially if `prefix_length` is set to `0`, because of the large number of variations of the word that OpenSearch tries to match. {: .warning} If [`search.allow_expensive_queries`]({{site.url}}{{site.baseurl}}/query-dsl/index/#expensive-queries) is set to `false`, fuzzy queries are not run. {: .important}