position: fixed caused element to be wider than browser

Question

Can anyone tell me why position:fixed cause the element to be wider than the browser or other content on the page and causing horizontal scrolling?

Here is the code HTML

Answer 1

The accepted answer is fine but in my case, I was seeing a fixed header that was wider than the rest of the page only on a mobile device. It happened to be caused by some element in the footer that had a width in pixels wider (width: 750px in my case) than the viewport of the browser.

If you want to know if some element on your page is causing this problem for you? Just open your browser console and remove some elements further down. At some point, you may notice the header becoming the correct width again. Chances are that the element you just removed or some element in it has a width in pixels wider than the viewport of the browser.

The solution, in that case, is to either set that element to a lesser width or make it flexible.