Я хочу обновить это приложение.

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Breakdown of Я хочу обновить это приложение.

• хотеть: to want
• этот: this
• приложение: the application

Questions & Answers about Я хочу обновить это приложение.

Why is it обновить and not обновлять here?

Russian verbs typically come in aspect pairs:

• обновлять – imperfective (ongoing, repeated, process)
• обновить – perfective (single, completed action, result)

With хотеть (to want), both aspects are possible, but they mean different things:

• Я хочу обновить это приложение.
  “I want to update this app (once, to get it up to date).”
  – Focus on the result: you want it to be updated.

• Я не люблю обновлять приложения.
  “I don’t like updating apps (in general).”
  – Focus on the activity / process in general.

In your sentence, you mean a single update that should be completed, so the perfective обновить is used.

What exactly does обновить mean? Is it only “to update (software)”?

Обновить is broader than just software. Literally it means “to make something new again”, “to renew,” “to refresh,” “to update.”

Examples:

• обновить приложение – to update an app
• обновить гардероб – to update/refresh one’s wardrobe
• обновить мебель – to replace/refresh the furniture
• обновить в памяти – to refresh in one’s memory

In modern tech contexts, обновить is the normal way to say “to update” (apps, programs, pages).