# locale.lang

Part of [Locale](https://kernstra.com/docs/web-sdk/config/locale) in the Kernstra Web SDK 1.0.0 configuration reference.

- Type: `string`
- Default: `'en'`
- Page: https://kernstra.com/docs/web-sdk/config/locale/lang

A BCP-47 tag, e.g. `'de-AT'`. It picks a table from `translations` and drives numbers and dates through `Intl`: zoom percentages, file sizes (the number; the unit is the `common.bytes.*` key, so French can say `Mo`), page counts, and dates in the signatures panel. Dates use the language's medium style ("Oct 7, 2026", "07.10.2026"); a signing time in the signatures panel shows the time the file records, not converted to the reader's time zone. Lists such as the Image tool's accepted types are joined the language's way ("PNG, JPEG, or GIF"). The viewer sets `lang` on its own element from this value, so screen readers pronounce the labels in that language; dialogs that open outside the viewer carry it too.

An invalid `lang` formats numbers and dates in English (a translation stored under exactly that string is still used). `lang` and the keys of `translations` are read in their canonical form (`de-at` becomes `de-AT`).

Web page: https://kernstra.com/docs/web-sdk/config/locale/lang