bɪkˈʌz ðɪ ɚɹˈɪdʒɪnəl tˈæb mˈɪks plˈʌs ɪz ɐ ˌɛksjˌuːˈɛlbˈeɪst ɛkstˈɛnʃən, ɪt dʌznˌɑːt wˈɜːk wɪð fˈaɪɚfɑːks fˈɪfti sˈɛvən ɔːɹ hˈaɪɚ.
Because the original Tab Mix Plus is a XUL-based extension, it does not work with Firefox 57 or higher.