Popup to Tab Converter от Mahsa Dinani

Popup to Tab Converter automatically detects popup windows that websites open using JavaScript's window.open() and converts them into a regular tab in your current browser window, instead of a separate floating window.

Why use it?
Many websites open login screens, payment flows, ad windows, or "share" dialogs in small popup windows. These extra windows clutter your taskbar, are easy to lose track of, and don't behave like normal tabs (no back/forward history integration, no easy tab switching). This add-on fixes that by seamlessly redirecting any popup into a tab.

How it works

Detects every new browser window of type "popup."
Reads the URL the popup is trying to load (waiting briefly if the page hasn't finished loading yet, e.g. about:blank popups).
Opens that URL as a new tab in your most recently used normal window.
Automatically closes the now-empty popup window.

Permissions

tabs — needed to read the popup's destination URL and to create/move tabs. The add-on does not collect, store, or transmit any personal data or browsing history.

Limitations

Only JavaScript-triggered popups (window.open()) are converted. Native browser "New Window" actions triggered manually by the user are not affected.
Some sites may briefly show the popup before it's converted to a tab, depending on how fast the page reports its URL.