Compatibility summary
Your Netherlands plug may fit in Eswatini outlets, as both use at least one common plug type.
Plug comparison
Netherlands plug types: C F
Eswatini plug types: C M N
Both countries share at least one plug type (C F and C M N), so some plugs may work without an adapter. Check your appliance.
Voltage comparison
Netherlands: 230V, 50Hz
Eswatini: 230V, 50Hz
Voltage difference is within a range many devices tolerate; check your appliance label.