Why is my phone simulating a wider screen resulution

The resulution width of the phone is 375px.

The phone shows a page of an app and it has a width of 980px.

This creates a zoom out effect making everything on the page smaller than it should be.

See screenshot from desktop-chrome with the iPhone 6 device turned on. It looks the same on the real device and on android etc.

Other pages work as expected.

Could be related to css.

Solution

I think you forgot to set your meta viewport tag (to this):

<meta name="viewport" content="width=device-width, initial-scale=1">