Reuse Tabs от Mike Turley

Prevents duplicate tabs. When you navigate to a URL that's already open in another tab (either by clicking a link or a new tab being opened from another app), the navigation is cancelled (or the new tab is closed) and you're switched to the existing tab instead.

Features

• Duplicate tab prevention — Intercepts navigations and new tabs, switching to the existing tab instead of creating a duplicate.
• External app handling — When an external app opens a URL that's already in a tab, the new tab is closed and the existing one is focused.
• Exempt duplicates — Right-click a tab and choose "Duplicate tab (exclude from Reuse Tabs)" to intentionally duplicate it. Exempt tabs are marked with a [D] title prefix and ignored by the extension.
• Reload on switch — Optionally reload stale tabs when switching to them, with a configurable idle timeout (1 min to 1 hour, or always).
• In-page toast notifications — See what the extension is doing with unobtrusive toast messages in the bottom-left corner of the page.
• Toolbar popup — Click the extension icon to toggle the extension on/off, enable/disable notifications, and configure reload behavior.

How it works

1. Maintains a cache of all open tab URLs, kept in sync via tab event listeners.
2. Uses webRequest.onBeforeRequest with blocking to intercept navigations before they happen.
3. If the target URL is already open in another tab, cancels the navigation and switches to that tab.
4. Tracks recently created tabs to catch duplicates opened by external apps and close the blank leftover tab.
5. Exempt tabs are tracked separately and skipped as switch targets, but navigation within them still triggers reuse logic.