[[lowercase-token-filter]]
=== In That Case

The most frequently used token filter is the lowercase filter, which does
exactly what you would expect; it transforms (((“tokens”, “normalizing”, “lowercase filter”)))(((“lowercase token filter”)))each token into its lowercase
form:

[source,js]

GET /_analyze?tokenizer=standard&filters=lowercase

The QUICK Brown FOX! <1>

<1> Emits tokens the, quick, brown, fox

It doesn’t matter whether users search for fox or FOX, as long as the same
analysis process is applied at query time and at search time. The lowercase
filter will transform a query for FOX into a query for fox, which is the
same token that we have stored in our inverted index.

To use token filters as part of the analysis process, we (((“analyzers”, “using token filters”)))(((“token filters”, “using with analyzers”)))can create a custom
analyzer:

[source,js]

PUT /my_index
{
“settings”: {
“analysis”: {
“analyzer”: {
“my_lowercaser”: {
“tokenizer”: “standard”,
“filter”: [ “lowercase” ]
}
}
}
}

}

And we can test it out with the analyze API:

[source,js]

GET /my_index/_analyze?analyzer=my_lowercaser

The QUICK Brown FOX! <1>

<1> Emits tokens the, quick, brown, fox