﻿---
title: Trim token filter
description: Removes leading and trailing whitespace from each token in a stream. While this can change the length of a token, the trim filter does not change a token’s...
url: https://www.elastic.co/elastic/docs-builder/docs/2437/reference/text-analysis/analysis-trim-tokenfilter
---

# Trim token filter
Removes leading and trailing whitespace from each token in a stream. While this can change the length of a token, the `trim` filter does *not* change a token’s offsets.
The `trim` filter uses Lucene’s [TrimFilter](https://lucene.apache.org/core/10_0_0/analysis/common/org/apache/lucene/analysis/miscellaneous/TrimFilter.md).
<tip>
  Many commonly used tokenizers, such as the [`standard`](https://www.elastic.co/elastic/docs-builder/docs/2437/reference/text-analysis/analysis-standard-tokenizer) or [`whitespace`](https://www.elastic.co/elastic/docs-builder/docs/2437/reference/text-analysis/analysis-whitespace-tokenizer) tokenizer, remove whitespace by default. When using these tokenizers, you don’t need to add a separate `trim` filter.
</tip>


## Example

To see how the `trim` filter works, you first need to produce a token containing whitespace.
The following [analyze API](https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-indices-analyze) request uses the [`keyword`](https://www.elastic.co/elastic/docs-builder/docs/2437/reference/text-analysis/analysis-keyword-tokenizer) tokenizer to produce a token for `" fox "`.
```json

{
  "tokenizer" : "keyword",
  "text" : " fox "
}
```

The API returns the following response. Note the `" fox "` token contains the original text’s whitespace. Note that despite changing the token’s length, the `start_offset` and `end_offset` remain the same.
```json
{
  "tokens": [
    {
      "token": " fox ",
      "start_offset": 0,
      "end_offset": 5,
      "type": "word",
      "position": 0
    }
  ]
}
```

To remove the whitespace, add the `trim` filter to the previous analyze API request.
```json

{
  "tokenizer" : "keyword",
  "filter" : ["trim"],
  "text" : " fox "
}
```

The API returns the following response. The returned `fox` token does not include any leading or trailing whitespace.
```json
{
  "tokens": [
    {
      "token": "fox",
      "start_offset": 0,
      "end_offset": 5,
      "type": "word",
      "position": 0
    }
  ]
}
```


## Add to an analyzer

The following [create index API](https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-indices-create) request uses the `trim` filter to configure a new [custom analyzer](https://docs-v3-preview.elastic.dev/elastic/docs-builder/docs/2437/manage-data/data-store/text-analysis/create-custom-analyzer).
```json

{
  "settings": {
    "analysis": {
      "analyzer": {
        "keyword_trim": {
          "tokenizer": "keyword",
          "filter": [ "trim" ]
        }
      }
    }
  }
}
```