It will stop working in Firefox Nightly tomorrow. It will continue working in normal Firefox until November, and in Firefox ESR until June next year. Tree Styl

It will stop working in Firefox Nightly tomorrow. It will continue working in normal Firefox until November, and in Firefox ESR until June next year. Tree Style Tabs itself will need to be redeveloped, but the necessary APIs are more or less available, and there are already similar add-ons that work in Firefox 57: - Tree Tabs: https://addons.mozilla.org/en-US/firefox/addon/tree-tabs/ https://addons.mozilla.org/en-US/firefox/addon/tree-tabs/ - Tab Center Redux: https://addons.mozilla.org/en-us/firefox/addon/tab-center-redux/ https://addons.mozilla.org/en-us/firefox/addon/tab-center-re... The most significant missing feature is the ability to hide the native, horizontal tab strip. That's being tracked in https://bugzil.la/1332447 https://bugzil.la/1332447.