JavaScript (ES2026) reference · String Methods

JavaScript String toLocaleLowerCase() Method

Convert to lowercase using a language's rules, which matters for languages like Turkish.

JavaScript (ES2026) Since ES3

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Syntax

string.toLocaleLowerCase(locales)

Parameter	Description
`locales` optional	A locale such as `"tr"`.

A new string.

Turkish dotless iTry it yourself

console.log("I".toLowerCase(), "I".toLocaleLowerCase("tr"));

Output

i ı

Accented lettersTry it yourself

console.log("ÉCOLE".toLocaleLowerCase("fr"));

Output

école

Version	Change
JavaScript ES3	Added

string.toLowerCase() · Return the string converted to lowercase. Use it for case-insensitive comparisons.
string.toLocaleUpperCase() · Convert to uppercase using a language's rules, for example Turkish or German special cases.
JavaScript Strings · tutorial
JavaScript String Methods · tutorial