use the left/right arrow keys to jump between pages
You can now use the arrow keys ← and → on your keyboard to navigate between pages on AO3.
It uses the first of whichever is encountered:
That means: If you're on the last chapter of work #2 in a series, pressing the right-arrow key will take you to work #3 in the series.
If you're on the first chapter, pressing the left-arrow key will take you to the previous work in the series.
If a work is part of multiple series, using the arrow keys isn't quite reliable because it will always use the first series in the metadata, and the order of the series in the metadata might switch between works.
It does not work for jumping through pages of comments on a work.
