OTA firmwares cannot be restored to. IPSW Downloads collects them for potential future use. They might also be useful if you're doing research.
| ✗ | Apple Watch Series 2 (38mm) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.3 GiB | b5b3fda90de86f8ab845bae56138b0a4a5be50f8.zip |
| ✗ | Apple Watch Series 2 (42mm) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.3 GiB | 2469552b5c76fde2ab3f7421694556498e5c39f2.zip |
| ✗ | Apple Watch Series 1 (38mm) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.3 GiB | 8c9efdf99fdc71ba4f5c086bc037795b336bfa42.zip |
| ✗ | Apple Watch Series 1 (42mm) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.3 GiB | c71743e83814078f27f964410c38133f3c2a7810.zip |
| ✗ | Apple Watch Series 3 (38mm, LTE) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.3 GiB | 66338985c6f965b07554283f6c476ded9c272148.zip |
| ✗ | Apple Watch Series 3 (42mm, LTE) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.3 GiB | 079f058cd6d01b949089a80d4b0171de7e232e00.zip |
| ✗ | Apple Watch Series 3 (38mm) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.3 GiB | e22e78a1072b14c5aa4f9d346f93bf923149dd3f.zip |
| ✗ | Apple Watch Series 3 (42mm) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.3 GiB | 026247342ecc5ba2e423792b2190e3e954a8dd6b.zip |
| ✗ | Apple Watch Series 4 (44mm) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.3 GiB | 3e3913a4b05f5bfdf24a913d71ab7b92e8eba92b.zip |
| ✗ | Apple Watch Series 4 (40mm) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.3 GiB | d1d2c2320b76c11282a9d62d24c3797afba02fb8.zip |
| ✗ | Apple Watch Series 4 (40mm, LTE) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.4 GiB | f2cb54a27fc4d859ca1bf3fcf685c97062559a45.zip |
| ✗ | Apple Watch Series 4 (44mm, LTE) | watchOS 5.3.6 (16U662) | March 24, 2020 | 1.3 GiB | d621d893309b89eee6d4375333566d7a794cadbb.zip |