This functionality is in beta and is subject to change. The design and code is considered to be less mature than official GA features. Elastic will take a best effort approach to fix any issues, but beta features are not subject to the support SLA of official GA features.

Normalizers are similar to analyzers except that they may only emit a single token. As a consequence, they do not have a tokenizer and only accept a subset of the available char filters and token filters. Only the filters that work on a per-character basis are allowed. For instance a lowercasing filter would be allowed, but not a stemming filter, which needs to look at the keyword as a whole.

Custom normalizersedit

Elasticsearch does not ship with built-in normalizers so far, so the only way to get one is by building a custom one. Custom normalizers take a list of char character filters and a list of token filters.

PUT index
  "settings": {
    "analysis": {
      "char_filter": {
        "quote": {
          "type": "mapping",
          "mappings": [
            "« => \"",
            "» => \""
      "normalizer": {
        "my_normalizer": {
          "type": "custom",
          "char_filter": ["quote"],
          "filter": ["lowercase", "asciifolding"]
  "mappings": {
    "type": {
      "properties": {
        "foo": {
          "type": "keyword",
          "normalizer": "my_normalizer"