Tags can be stored externally, or in industry-standard IPTC or XMP headers inside each image file or in sidecar files.
tˈæɡz kæn biː stˈoːɹd ɛkstˈɜːnəli, ɔːɹ ɪn ˈɪndʌstɹistˈændɚd ˈɪptk ɔːɹ ˌɛksˌɛmpˈiː hˈɛdɚz ɪnsˈaɪd ˈiːtʃ ˈɪmɪdʒ fˈaɪl ɔːɹ ɪn sˈaɪdkɑːɹ fˈaɪlz.