Save Wikipedia Settings by iissmart

Wikipedia stores your appearance settings - text size, width, color, and whether the appearance panel sits in the sidebar - in a cookie that lasts 30 days and is only refreshed when you change something. Once it expires, every article snaps back to standard text, standard width, light color, and a visible panel, and you set all four again.

This add-on fixes that two ways:

• It rewrites the preference cookie on every visit, so the 30-day window never runs out.
• It applies your settings before the page renders, so an article that has already lapsed still looks right, with no flash of the old appearance.

Pick your settings from the toolbar popup, using the same choices as Wikipedia's own Appearance menu:

• Text size: Small, Standard, Large
• Width: Standard, Wide
• Color: Automatic, Light, Dark
• Appearance panel: shown in the sidebar, or hidden

It defaults to small, wide, dark, and hidden. Changes apply to open Wikipedia tabs immediately.

Signed in to Wikipedia? The add-on steps out of the way. Your account already carries your appearance settings, so the extension detects that and leaves those pages untouched.

Wikipedia's own Appearance menu still works normally on the page in front of you. The add-on stops enforcing once a page has finished loading, so you can try a different setting without it being snapped back. The next page load returns to your saved choices.

Permissions and privacy: it runs only on wikipedia.org, keeps your four preferences in local browser storage, and collects nothing. It requests a single permission, storage. No network requests, no analytics, no accounts.

Source: https://github.com/iissmart/firefox-wikipedia-save-settings