PhoneVitals › Restore error codes › Error 21
iPhone restore error 21
What iTunes and Finder are actually telling you, and which component to look at first.
Error 21
Check the battery / battery connector — Restore power/authentication handshake fails - very commonly dead, disconnected or aftermarket battery / battery connector; Apple lists as hardware
Most likely: BatteryStop guessing which part failed
PhoneVitals reads the phone's own telemetry over USB and names the failing component with the evidence attached — battery gauge records, decoded kernel panics, board-level suspects. Your first device scan is free.
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