umschalten
to switch channels
To change the channel on a television or radio.
Schalt bitte um, die Sendung ist langweilig.
Please switch channels; the show is boring.

to switch
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to switch channels
To change the channel on a television or radio.
Schalt bitte um, die Sendung ist langweilig.
Please switch channels; the show is boring.

'Umschalten' (to switch) is a separable verb. The prefix 'um-' comes at the end in a main clause. In subordinate clauses and in the infinitive with 'zu', the verb stays together.
Ich schalte schnell auf ein anderes Programm um.
I'll quickly switch to another program.
When you want to specify what you are switching to, the preposition 'auf' with the accusative is used. This pattern applies to all meanings of the word.
Könntest du bitte auf den Nachrichtenkanal umschalten?
Could you please switch to the news channel?
In addition to the technical meaning, 'umschalten' is often used metaphorically for a mental shift. For example, you can mentally 'switch' from one topic to another or from leisure time to work.
Es fällt mir schwer, nach dem Wochenende mental wieder umzuschalten.
I find it hard to mentally switch back after the weekend.
This meaning is typical of technical language in sports, especially soccer. It describes the quick transition between attacking and defensive play.
Die Mannschaft ist bekannt dafür, nach einem Ballverlust langsam umzuschalten.
The team is known for transitioning slowly after losing the ball.
to change / switch
'wechseln' and 'umschalten' both have to do with switching from one state or program to another. 'wechseln' is more general and fits many areas, for example topic, seat, task, or channel. 'umschalten' is used especially with devices when you change the channel, mode, or a setting. It can also be used figuratively to mean that you quickly change your focus or way of thinking. Learners confuse the words because with a television you can say both 'den Sender wechseln' and 'umschalten' (change/switch channels). With buttons, technology, and modes, 'umschalten' often sounds more natural.

Meine Schwester schaltet den Laptop in den Nachtmodus um.
My sister switches the laptop to night mode.
Beim Kochen wechselt Tom den Radiosender.
While cooking, Tom changes the radio station.