---
layout: default
title: Prefix
parent: Term-level queries
nav_order: 60
---

# Prefix query

Use the `prefix` query to search for terms that begin with a specific prefix. For example, the following query searches for documents in which the `speaker` field contains a term that starts with `KING H`:

```json
GET shakespeare/_search
{
  "query": {
    "prefix": {
      "speaker": "KING H"
    }
  }
}
```
{% include copy-curl.html %}

To provide parameters, you can use a query equivalent to the preceding one with the following extended syntax:

```json
GET shakespeare/_search
{
  "query": {
    "prefix": {
      "speaker": {
        "value": "KING H"
      }
    }
  }
}
```
{% include copy-curl.html %}


## Parameters

The query accepts the name of the field (`<field>`) as a top-level parameter:

```json
GET _search
{
  "query": {
    "prefix": {
      "<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>`.
`boost` | Floating-point | A floating-point value that specifies the weight of this field toward the relevance score. Values above 1.0 increase the field’s relevance. Values between 0.0 and 1.0 decrease the field’s relevance. Default is 1.0.
`case_insensitive` | Boolean | If `true`, allows case-insensitive matching of the value with the indexed field values. Default is `false` (case sensitivity is determined by the field's mapping).
`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`.

If [`search.allow_expensive_queries`]({{site.url}}{{site.baseurl}}/query-dsl/index/#expensive-queries) is set to `false`, then prefix queries are not executed. If `index_prefixes` is enabled, then the `search.allow_expensive_queries` setting is ignored and an optimized query is built and run.
{: .important}