They speak German, but not exactly

The thing about Liechtenstein you should know is that Liechtenstein's official language is German, and the principality is the smallest of the four countries in Europe populated by a majority of German speakers. Other languages are also spoken by the foreign-born population, which makes up about 14% of the country (and two-thirds of the workforce).

Although German is the country’s official language, most residents speak an Alemannic dialect that’s very different from standard German and closer to Swiss Standard German. Alemannic dialect: spoken by most Liechtensteiners, it is different from Standard German but closely related to dialects spoken in neighboring regions such as Switzerland and Vorarlberg, Austria. In Triesenberg, a Walser German dialect promoted by the municipality is spoken. Swiss Standard German is also understood and spoken by most Liechtensteiners. As such, the country is usually referred to as Liechtenstein, not Liechtenstein, by its citizens.