All German-speaking countries share the same literary language with a few minor differences in vocabulary and some minor differences in spelling conventions. These aside, The German of Germany, Austria, and Switzerland is much less different than British and American English.
BUT this only concerns the written language- dialects are spoken on a continuum in all German-speaking countries, although in Austria and Germany, there has been a strong tendency to drop dialects and speak only Hochdeutsch. Regional accents are the biggest giveaway here (although dialects are not dead at all and do continue to be used).
The Swiss, on the other hand, have gone the other way and dialect is used almost exclusively in daily life. All the Swiss dialects are Alemannic, and these have some continuities with some of the West Austrian and South-West German accents but each dialect in Switzerland also has distinct features. İn other words, the spoken language of Bern is not the same as that of Zürich, or Graubünden.
Nonetheless, all Swiss German speakers can also speak Hochdeutsch when needed and are effectively diglossic.
