HotmailTabs was a Firefox extension developed by Palancar in the mid-2000s that solved a very specific frustration with webmail of that era: clicking a “Compose” or “Reply” link in Hotmail (or any webmail of similar architecture) would open a new browser window instead of a new tab. For users running Firefox specifically because of its tabbed-browsing model, that was a constant irritation. HotmailTabs hijacked the window-spawning behavior of those webmail links and rerouted them into tabs.
What HotmailTabs Did
The extension hooked into Firefox’s window-opening event chain and identified window.open() calls from Hotmail’s compose buttons and similar webmail links. Rather than allowing a new top-level browser window to spawn, it intercepted the call and used gBrowser.addTab() (Firefox’s internal tab-opening API in the XUL era) to load the target URL in a tab adjacent to the current one. This worked because Hotmail’s compose flow relied on conventional window.open() JavaScript that the browser could intercept before delegating to the OS window manager.
Internally, the extension used a content-policy listener pattern — registering with nsIContentPolicy to evaluate each window-opening attempt and rewriting the destination from “new window” to “new tab” when the source matched configured webmail domains.
Why It’s No Longer Needed
Two changes made HotmailTabs obsolete. First, Mozilla added native control of window-versus-tab behaviour to Firefox’s built-in tab preferences — most settings that HotmailTabs handled became toggles in the browser. Second, modern webmail (Gmail, Outlook on the Web, the modernized Hotmail successor) generally doesn’t use top-level window.open() for compose anymore — these UIs are SPA-style and handle their own panel/modal/tab logic internally.
The extension also did not survive the Firefox 57 WebExtensions transition. The new API doesn’t allow hooking the window-creation pipeline the way HotmailTabs did — modern equivalent functionality is more limited and typically handled by the browser’s built-in preferences.
Historical Snapshot
The Wayback Machine archive of palancar.net preserves snapshots of the original HotmailTabs page from the active period.