Font sizes on Super User are way to big on mobile devices (or, more specifically: viewports with widths up to 640 px). This does not affect all Stack Exchange sites, it’s a problem with the Super User theme.

Super User vs Meta

The problem appears to stem from a bad interaction with the <body> font size and other elements referencing it using the rem unit.

On Meta, the font size is simply 11px. However, on Super User, it is calc(var(--su-static12) - var(--su-static1)). Dunno what’s the point, the result (when looking at calculated values) is also 11 px. Either way, the result is very different.

I can see the issue in the following environments:

  • Firefox simulated mobile view (origin of screenshots above)
  • Edge simulated mobile view
  • Safari in iOS

I suggest sticking with a 11px here, the calc() stuff seems pointless to me.

  • Meta.SE duplicate: meta.stackexchange.com/questions/391579/… From experience clearing your caches on mobile can fix it.
    – Mokubai Mod
    Jul 27, 2023 at 19:47
  • Nope, Super User is still pulling the CSS that causes this. // But good to know the fix is already on its way.
    – Daniel B
    Jul 27, 2023 at 19:50
  • Weird. Firefox mobile was faulty for me yesterday and literally fixed after clearing caches. Maybe a "simulated view" problem?
    – Mokubai Mod
    Jul 27, 2023 at 19:52
  • Maybe German traffic is handled on a different node in the CDN or something.
    – Daniel B
    Jul 27, 2023 at 19:54
  • Can confirm - I saw the original issue on SO and saw it fixed, but I can still reproduce this in SU. Curiously, this happens with my Samsung Internet browser, but not with Chrome or Firefox on the same phone. My gut instinct says "caching", but no amount of refresh/restarts solves this.
    – Mureinik
    Jul 30, 2023 at 8:33
  • For the record: Also still happening over here. Maybe the version in the URL needs to be updated or something? Even when I fetch the CSS using curl, I still get the buggy version.
    – Daniel B
    Jul 30, 2023 at 9:27
  • Adding a datapoint regarding CDNs - I'm from Israel. I observed this behavior both on my mobile network and from my home's wifi (although they probably use the same CDN)
    – Mureinik
    Jul 31, 2023 at 9:30
  • This seems to be resolved now
    – Mureinik
    Aug 2, 2023 at 18:58

1 Answer 1


The fix discussed on Meta is finally live where I live. Hopefully the rest of the world also has it!

tl;dr: This bug has been patched in our design system and the update has been shipped to production.

Good catch @0stone0!

This was due to a change to some font-size values to replace explicit pixel values with calculated values based on custom properties. To be honest, I'm not sure why the calculated values cause this issue and explicit pixel values don't. Nevertheless, changing back to explicit pixel values resolves the issue.

Note: The cache on each network site needs to clear individually, so this may take a few days to be reflected.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .