elasticsearch/docs/reference/elasticsearch-plugins/analysis-icu-normalization.md
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Co-authored-by: Liam Thompson <32779855+leemthompo@users.noreply.github.com>
Co-authored-by: Liam Thompson <leemthompo@gmail.com>
Co-authored-by: Martijn Laarman <Mpdreamz@gmail.com>
Co-authored-by: István Zoltán Szabó <szabosteve@gmail.com>
2025-02-27 17:56:14 +01:00

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Markdown

---
mapped_pages:
- https://www.elastic.co/guide/en/elasticsearch/plugins/current/analysis-icu-normalization.html
---
# ICU normalization token filter [analysis-icu-normalization]
Normalizes characters as explained [here](https://unicode-org.github.io/icu/userguide/transforms/normalization/). It registers itself as the `icu_normalizer` token filter, which is available to all indices without any further configuration. The type of normalization can be specified with the `name` parameter, which accepts `nfc`, `nfkc`, and `nfkc_cf` (default).
Which letters are normalized can be controlled by specifying the `unicode_set_filter` parameter, which accepts a [UnicodeSet](https://icu-project.org/apiref/icu4j/com/ibm/icu/text/UnicodeSet.md).
You should probably prefer the [Normalization character filter](/reference/elasticsearch-plugins/analysis-icu-normalization-charfilter.md).
Here are two examples, the default usage and a customised token filter:
```console
PUT icu_sample
{
"settings": {
"index": {
"analysis": {
"analyzer": {
"nfkc_cf_normalized": { <1>
"tokenizer": "icu_tokenizer",
"filter": [
"icu_normalizer"
]
},
"nfc_normalized": { <2>
"tokenizer": "icu_tokenizer",
"filter": [
"nfc_normalizer"
]
}
},
"filter": {
"nfc_normalizer": {
"type": "icu_normalizer",
"name": "nfc"
}
}
}
}
}
}
```
1. Uses the default `nfkc_cf` normalization.
2. Uses the customized `nfc_normalizer` token filter, which is set to use `nfc` normalization.