Windows System Errors
Windows System Errors 21 — ERROR_NOT_READY
In Windows System Errors, code 21 is ERROR_NOT_READY. The official source describes it as “The device is not ready.”. Its concrete cause depends on the operation and surrounding message.
Code21
SymbolERROR_NOT_READY
Source confidencehigh
Official definition
The device is not ready.
In plain language
In Windows System Errors, code 21 is ERROR_NOT_READY. The official source describes it as “The device is not ready.”. Its concrete cause depends on the operation and surrounding message.
Context to inspect
- The surrounding operation, version and subsystem determine the actual cause.
- The same numeric value can mean something different in another namespace.
Safe first checks
- Confirm which product, protocol or subsystem produced the code.
- Read the full surrounding error message and inspect relevant logs.
- Compare the code with the linked authoritative documentation before changing configuration.
Important context
The surrounding operation, version and subsystem determine the actual cause.