Does this respect the user's locale for number formatting?

Yes, pretty-bytes respects the user's locale for number formatting through the locale option.

The locale option accepts multiple formats [index.d.ts:L10-L18]:

• false (default): Output won't be localized
• true: Localize using the system/browser locale
• string: A specific BCP 47 language tag (e.g., 'de', 'en')
• string[]: A list of BCP 47 language tags to try in order

The implementation uses the toLocaleString function [index.js:L55-L65], which delegates to JavaScript's native Number#toLocaleString() method. This applies locale-specific formatting to both the number itself and the decimal separator.

For example [test.js:L71-L110]:

• German locale ('de'): prettyBytes(1001, {locale: 'de'}) returns '1 kB' with a comma decimal separator
• English locale ('en'): prettyBytes(1001, {locale: 'en'}) returns '1 kB' with a period decimal separator

Important caveat [readme.md:L122-L124]: Only the number and decimal separator are localized. The unit titles (like 'kB', 'MB') are not localized and remain in English.

FOLLOW_UPS:

• How does the fixedWidth option work for alignment?
• What's the difference between binary and SI prefix formatting?
• Can you use both locale and minimumFractionDigits together?