From Wikipedia:
Unlike most regional languages in modern Europe, Swiss German is the spoken everyday language of all social levels in industrial cities, as well as in the countryside. Using dialect conveys neither social nor educational inferiority and is done with pride.[1] There are only a few specific settings where speaking Standard German is demanded or polite, e.g., in education (but not during breaks in school lessons, where the teachers will speak in dialect with students), in multilingual parliaments (the federal parliaments and a few cantonal and municipal ones), in the main news broadcast or in the presence of German-speaking foreigners. This situation has been called a "medial diglossia", since the spoken language is mainly the dialect, whereas the written language is mainly Standard German.
Swiss German is intelligible to speakers of other Alemannic dialects, but poses greater difficulty in total comprehension to speakers of Standard German, including French- or Italian-speaking Swiss who learn Standard German at school. Swiss German speakers on TV or in movies are thus usually dubbed or subtitled if shown in Germany.