Tab Deduper от nosoop

A minimal alternative for Duplicate Tabs Closer.
It used to be a replacement, but the author of that plugin has also migrated it to WebExtensions.

Good for tab hoarders that open new tabs to revisit sites they might already have tabs open for.

Whenever a tab's URL changes, it is checked against the current window's existing tabs. On a match, one is made active and the other is removed.

There are a few options to control the behavior.