Below you can find the direct links to the iPhone Firmware Files for every released firmware version of iOS. Please note that if you use Safari for your iOS download, you must disable the auto unzip feature. It may be easier to just use Firefox!
Latest:
15.5 (6s): iPhone_4.7_15.5_19F77_Restore.ipsw
15.5 (6s+): iPhone_5.5_15.5_19F77_Restore.ipsw
15.5 (SE): iPhone_4.0_64bit_15.5_19F77_Restore.ipsw
15.5 (7 GSM+CDMA): iPhone_4.7_P3_15.5_19F77_Restore.ipsw
15.5 (7+ GSM+CDMA): iPhone_5.5_P3_15.5_19F77_Restore.ipsw
15.5 (8 GSM+CDMA): iPhone_4.7_P3_15.5_19F77_Restore.ipsw
15.5 (8 Plus GSM+CDMA): iPhone_5.5_P3_15.5_19F77_Restore.ipsw
15.5 (X GSM+CDMA): iPhone10,3,iPhone10,6_15.5_19F77_Restore.ipsw
15.5 (XS): iPhone11,2,iPhone11,4,iPhone11,6,iPhone12,3,iPhone12,5_15.5_19F77_Restore.ipsw
15.5 (XS Max (China)): iPhone11,2,iPhone11,4,iPhone11,6,iPhone12,3,iPhone12,5_15.5_19F77_Restore.ipsw
15.5 (XS Max (Global)): iPhone11,2,iPhone11,4,iPhone11,6,iPhone12,3,iPhone12,5_15.5_19F77_Restore.ipsw
15.5 (XR): iPhone11,8,iPhone12,1_15.5_19F77_Restore.ipsw
15.5 (11): iPhone11,8,iPhone12,1_15.5_19F77_Restore.ipsw
15.5 (11 Pro): iPhone11,2,iPhone11,4,iPhone11,6,iPhone12,3,iPhone12,5_15.5_19F77_Restore.ipsw
15.5 (11 Pro Max): iPhone11,2,iPhone11,4,iPhone11,6,iPhone12,3,iPhone12,5_15.5_19F77_Restore.ipsw
15.5 (SE 2): iPhone12,8_15.5_19F77_Restore.ipsw
15.5 (12 mini): iPhone13,1_15.5_19F77_Restore.ipsw
15.5 (12): iPhone13,2,iPhone13,3_15.5_19F77_Restore.ipsw
15.5 (12 Pro): iPhone13,2,iPhone13,3_15.5_19F77_Restore.ipsw
15.5 (12 Pro Max): iPhone13,4_15.5_19F77_Restore.ipsw
15.5 (13 Pro): iPhone14,2_15.5_19F77_Restore.ipsw
15.5 (13 Pro Max): iPhone14,3_15.5_19F77_Restore.ipsw
15.5 (13 mini): iPhone14,4_15.5_19F77_Restore.ipsw
15.5 (13): iPhone14,5_15.5_19F77_Restore.ipsw
15.5 (SE 3): iPhone14,6_15.5_19F77_Restore.ipsw