Duplicate Tab Controller

Rule-based duplicate tab controller (Chrome / Firefox, MV3)

A tab manager that lets you decide how each site's duplicates are handled, instead of blindly closing every duplicate. Perfect when you want to be asked on open, yet still keep as many localhost or specific-site tabs as you like. ● Confirm on open When you open a duplicate, a small toast lets you choose: Switch to existing / Close the new one / Keep both. It appears on the tab you're actually looking at, so you won't miss duplicates opened in the background. ● Per-site rules ・Allow multiples: keep localhost, dashboards, etc. openable any number of times ・Auto-switch: always keep one — opening a duplicate switches to the existing tab and closes the new one ・Confirm / Auto-close / Ignore are also available The first matching rule from the top wins. Add rules in one click from the popup or the toast. ● Spot duplicates at a glance Duplicate tabs get a red line under the favicon. Your tabs are never reordered. ● Duplicate tab list Open the toolbar icon to see all current duplicates and switch, close them individually, or close a whole group. The tab you're on comes first. ● Fine-grained control ・URL normalization (hash / query / www / trailing slash / http=https / ignore specific query keys, …) ・Protection: pinned, audio-playing, and tabs with active form input are never auto-closed ・"Pin" a single tab to exclude just that tab; pause the whole extension ・Developer mode: allow multiple tabs for localhost and other dev URLs ● Privacy No browsing history or personal data is collected or sent anywhere. Your settings are stored in the browser only, with no communication to any external server. Available in Japanese and English.