Can I update my iPhone 6s Plus to iOS 13 or later?

Update your iPhone, iPad, or iPod touch - Apple Support

If you’re trying to update to iOS 13 or later (15.4.1 is current), you’ll probably want to use (or borrow and use) a Mac or Windows computer for the update, given how far back your iPhone seems to be. How to do this is included in the linked “update” article.

You must have a stable Wi-Fi connection.

Or connect to a PC with the latest version of iTunes installed.

Charge the battery to 50% or higher.

Turn off Battery saving mode.

Don't use a Hotspot.

Don't use VPN.



And make sure you have enough free space.