---
title: ASCII Folding
---

The ASCII folding filter strips away diacritical marks (accents, umlauts, tildes, etc.) while leaving the base character intact.
It is supported for all tokenizers besides the [literal](/v2/tokenizers/available_tokenizers/exact) tokenizer.

To enable, append `ascii_folding=true` to the tokenizer's arguments.

```sql
CREATE INDEX search_idx ON mock_items
USING bm25 (id, (description::pdb.simple('ascii_folding=true')))
WITH (key_field='id');
```

To demonstrate this token filter, let's compare the output of the following two statements:

```sql
SELECT
  'Café naïve coöperate'::pdb.simple::text[],
  'Café naïve coöperate'::pdb.simple('ascii_folding=true')::text[];
```

```ini Expected Response
          text          |          text
------------------------+------------------------
 {café,naïve,coöperate} | {cafe,naive,cooperate}
(1 row)
```
