Foobar was one of the earlier Firefox extensions developed and distributed from palancar.net during the Firefox 1.x and 2.x era. Like several Palancar-era extensions, it operated through the XUL (XML User Interface Language) overlay system that Firefox used before the WebExtensions API rewrite. Extensions in this period had direct access to the browser’s chrome UI and could inject menus, toolbars, and behaviour modifications at a level no modern extension can reach.
Foobar specifically focused on context-menu and toolbar customization — letting users add or rearrange common interface elements without editing about:config or learning XUL itself. For a stretch of years it appeared in Firefox-customization roundups alongside contemporaries like Tabbrowser Extensions, ChromEdit, and the Stylish CSS framework.
Why It’s No Longer Active
Like the rest of the Palancar Firefox extension catalog, Foobar did not survive the WebExtensions transition in Firefox 57 (the November 2017 “Quantum” release). Mozilla deprecated the XUL/XPCOM extension model entirely, requiring every extension to migrate to the new WebExtensions API or stop working. Many one-developer extensions from the mid-2000s — Foobar among them — were not rewritten for the new model.
Modern Equivalents
For modern UI customization, the WebExtensions API supports browser.menus for context-menu modification and browser.action for toolbar button placement. Direct chrome modification of the kind Foobar performed is no longer permitted — the WebExtensions sandbox is one of the security improvements that came with Quantum.
For a sense of what the original Foobar page looked like during its active period, the Wayback Machine archive of palancar.net preserves snapshots from 2005 through 2012.