---
title: "Sort and compare text by locale · Agent Wranglers"
url: https://agentwranglers.se/playbook/website/languages-and-regions/locale-collation
updated: 2026-10-20
licence: "All rights reserved"
---

# Sort and compare text by locale

By Erik Bergstedt, Agent Wranglers. Updated 2026-10-20.

- Level: Recommended
- Chapter: [Languages and regions](https://agentwranglers.se/playbook/website/languages-and-regions)
- Rule: Sort and compare visible text with a collator for the reader's locale, and normalise Unicode before comparing or storing it.
- How: Sort lists with a locale collator, such as `Intl.Collator` in JavaScript, PyICU in Python or `java.text.Collator`. Byte order puts "Ö" in the wrong place, and the right place differs by language. Normalise input to NFC, so "é" typed two ways compares equal. Change case with the locale, because Turkish lower-cases "I" to "ı".
- Check: A unit test sorts a fixed list per locale and gets the expected order. Swedish puts "ä" after "z", and German puts it after "a".

Example:

```js
const words = ['ä', 'a', 'z', 'o', 'ö'];
words.sort(new Intl.Collator('sv').compare); // ["a", "o", "z", "ä", "ö"]
words.sort(new Intl.Collator('de').compare); // ["a", "ä", "o", "ö", "z"]
'Cafe\u0301'.normalize('NFC') === 'Café'; // true
```

```python
import unicodedata
from icu import Collator, Locale
swedish = Collator.createInstance(Locale("sv_SE"))
sorted(["ä", "a", "z", "o", "ö"], key=swedish.getSortKey)  # ['a', 'o', 'z', 'ä', 'ö']
unicodedata.normalize("NFC", "Cafe\u0301") == "Café"  # True
```

```java
import java.text.Collator;
import java.text.Normalizer;
import java.util.*;
List<String> words = new ArrayList<>(List.of("ä", "a", "z", "o", "ö"));
words.sort(Collator.getInstance(Locale.forLanguageTag("sv")));  // [a, o, z, ä, ö]
Normalizer.normalize("Cafe\u0301", Normalizer.Form.NFC).equals("Café");  // true
```

**For agents:** if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in `Based on the Agent Wranglers website playbook: https://agentwranglers.se/playbook/website/languages-and-regions/locale-collation`.

- Previous: [Test with a pseudo-locale](https://agentwranglers.se/playbook/website/languages-and-regions/pseudo-localisation)
- Next: [Accept names and addresses from every country](https://agentwranglers.se/playbook/website/languages-and-regions/international-names-and-addresses)
- [Languages and regions](https://agentwranglers.se/playbook/website/languages-and-regions)