I can't update my Mac , when I open software update there is no new update , my Mac version is10.13.6

Back up your data, check your applications for compatibility, and depending on which Mac model you have, click on Mojave, Catalina, Big Sur, or Monterey. They're full-version upgrades and won't appear in the Updates list.

If you try to upgrade to Mojave through Big Sur and get a 'Cannot connect' error message or the Mac App Store home page, wait a few hours and check again.

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That means that your current operating system is up to date. What you want to do is to upgrade (not update) your operating system to a newer version.. Use the links provided above to do so. It is important to understand that updates and upgrades are not the same things.

Update your iPhone, iPad, or iPod touch

If nothing is offered by Apple - the iPhone is running the last version of iOS it Qualifies to run.

update softver iphone 4s