My windows 10 taskbar icon width is so wide

Update I've found out how to switch this off!

  1. Go to Settings (e.g. [Win]+I), then System, then Tablet; or hit [Win] and type "Tablet settings" to go straight there.
  2. Click "Change additional tablet settings"
  3. Under "When I'm not in tablet mode", set "Make app icons on the taskbar easier to touch" to off

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Original answer

Are you using a 2-in-1 PC in "tent" mode (maybe with an external keyboard and mouse)?

According to WinCentral, It appears this is a new "feature" in version 2004 (aka 20H1) for 2-in-1 PCs to make it easier to use the touch screen when not using as a "normal" laptop.

I'm afraid I've not found out how to turn it off yet, but it's REALLY annoying!

The only work-around that I can find is to flip your laptop over and use it as a conventional laptop - the icons return to normal size.