Smaller PDF pages are not centered correctly after zooming out in Split View

Rence_k — Thu, 06 Aug 2026 19:47:27 GMT

Hi,

I found a very specific issue with the Firefox PDF viewer. It is not easy to reproduce.

It happens with some PDF books where the first page (usually the cover) is much larger than the other pages.

Steps to reproduce:

1. Open a PDF book with a large first page/cover.
2. Open it in Firefox Split View.
3. Go to a normal text page after the cover (a smaller page).
4. Zoom out.

What happens:
The smaller text pages are no longer correctly centered after zooming out.

The page looks centered only when the horizontal scrollbar is completely on the left.

If I move the scrollbar to the middle, the page shifts to the left instead of remaining centered.

The problem seems to affect the smaller pages after a larger first page. The cover itself is not the issue.

Expected behavior:
Each page should stay centered according to its own size. The size of the cover should not affect the position of the following smaller pages.

Tested:

Firefox 153.0.3
Happens with different PDF books
Still happens with a new Firefox profile
Changing zoom options does not fix it

It looks like Firefox keeps something from the larger cover page and does not correctly position the smaller pages after zooming out.

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Smaller PDF pages are not centered correctly after zooming out in Split View