---
navigation_title: "Remove duplicates"
mapped_pages:
  - https://www.elastic.co/guide/en/elasticsearch/reference/current/analysis-remove-duplicates-tokenfilter.html
---

# Remove duplicates token filter [analysis-remove-duplicates-tokenfilter]


Removes duplicate tokens in the same position.

The `remove_duplicates` filter uses Lucene’s [RemoveDuplicatesTokenFilter](https://lucene.apache.org/core/10_0_0/analysis/common/org/apache/lucene/analysis/miscellaneous/RemoveDuplicatesTokenFilter.html).

## Example [analysis-remove-duplicates-tokenfilter-analyze-ex]

To see how the `remove_duplicates` filter works, you first need to produce a token stream containing duplicate tokens in the same position.

The following [analyze API](https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-indices-analyze) request uses the [`keyword_repeat`](/reference/text-analysis/analysis-keyword-repeat-tokenfilter.md) and [`stemmer`](/reference/text-analysis/analysis-stemmer-tokenfilter.md) filters to create stemmed and unstemmed tokens for `jumping dog`.

```console
GET _analyze
{
  "tokenizer": "whitespace",
  "filter": [
    "keyword_repeat",
    "stemmer"
  ],
  "text": "jumping dog"
}
```

The API returns the following response. Note that the `dog` token in position `1` is duplicated.

```console-result
{
  "tokens": [
    {
      "token": "jumping",
      "start_offset": 0,
      "end_offset": 7,
      "type": "word",
      "position": 0
    },
    {
      "token": "jump",
      "start_offset": 0,
      "end_offset": 7,
      "type": "word",
      "position": 0
    },
    {
      "token": "dog",
      "start_offset": 8,
      "end_offset": 11,
      "type": "word",
      "position": 1
    },
    {
      "token": "dog",
      "start_offset": 8,
      "end_offset": 11,
      "type": "word",
      "position": 1
    }
  ]
}
```

To remove one of the duplicate `dog` tokens, add the `remove_duplicates` filter to the previous analyze API request.

```console
GET _analyze
{
  "tokenizer": "whitespace",
  "filter": [
    "keyword_repeat",
    "stemmer",
    "remove_duplicates"
  ],
  "text": "jumping dog"
}
```

The API returns the following response. There is now only one `dog` token in position `1`.

```console-result
{
  "tokens": [
    {
      "token": "jumping",
      "start_offset": 0,
      "end_offset": 7,
      "type": "word",
      "position": 0
    },
    {
      "token": "jump",
      "start_offset": 0,
      "end_offset": 7,
      "type": "word",
      "position": 0
    },
    {
      "token": "dog",
      "start_offset": 8,
      "end_offset": 11,
      "type": "word",
      "position": 1
    }
  ]
}
```


## Add to an analyzer [analysis-remove-duplicates-tokenfilter-analyzer-ex]

The following [create index API](https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-indices-create) request uses the `remove_duplicates` filter to configure a new [custom analyzer](docs-content://manage-data/data-store/text-analysis/create-custom-analyzer.md).

This custom analyzer uses the `keyword_repeat` and `stemmer` filters to create a stemmed and unstemmed version of each token in a stream. The `remove_duplicates` filter then removes any duplicate tokens in the same position.

```console
PUT my-index-000001
{
  "settings": {
    "analysis": {
      "analyzer": {
        "my_custom_analyzer": {
          "tokenizer": "standard",
          "filter": [
            "keyword_repeat",
            "stemmer",
            "remove_duplicates"
          ]
        }
      }
    }
  }
}
```