AO3 Filter Manager per willhansen

AO3 work filters — sort, ratings, warnings, categories, word count, language,
include/exclude tag lists — reset every time you click through to a new tag.
AO3 Filter Manager carries them with you, and adds named, reusable filter
sets.


Carry filters between tags — Set your filters once, then click any tag
link on the page; the new tag's works listing opens with the same filters
already applied. Middle-click and Ctrl+click (new tabs) work too, and you
always land on page 1 of the new tag. Landing on an unfiltered listing —
including via AO3's own "Clear Filters" link — resets the carry, so filters
you deliberately dropped stay dropped. Carry can be toggled off in the panel.

A panel for your filters — A small "AO3 Filters" button (bottom-right
corner) opens a manager panel that:

• lists every active filter in plain English ("Sort: Kudos", "Exclude
  Warning: Major Character Death", "Fandom: Doctor Who (2005)") with a ×
  button to remove filters one at a time
• offers a one-click "Clear all filters"
• stays open across pages while you navigate from tag to tag

Named filter sets — Save the current filter combination under any name,
then apply it with one click to any works listing: a tag's works page, the
Works index, or works search. Overwriting and deleting sets is supported.

Export / Import — Export all saved sets to a JSON file and import them
into another browser or share them with a friend. Imported sets that clash
with existing names are renamed automatically.

1. Set filters on a works listing as you normally would, using AO3's sidebar
   filter form.
2. Click any tag link — your filters come along automatically.
3. Click AO3 Filters (bottom right) to review filters, remove them one
   by one, clear them, or save the combination as a set.
4. On any works listing, open the panel and hit Apply to this listing
   on a saved set.

• Handles AO3's canonical-tag redirect quirk: AO3 drops the whole query
  string when redirecting a non-canonical tag to its canonical form; AO3
  Filter Manager detects this and restores your filters automatically.
• Tag names are learned locally from AO3's own filter forms, so saved sets
  read "Fandom: Doctor Who (2005)" instead of raw tag IDs; rating, warning,
  category, sort, and language labels are scraped from those same forms
  instead of being hardcoded, so the panel always matches AO3's wording.
• Respects the adult-content gate once you've passed it, so carried links
  don't bounce you back to the interstitial.
• Everything is stored in your browser (localStorage). No network requests,
  no accounts, no external assets, no dependencies, and no privileges
  beyond the AO3 site itself.
• Works on works listings: tag works pages, the Works index (/works), and
  works search.