A key code is a series of alphanumeric characters used by locksmiths to create a key. There are two kinds of key codes: blind codes and bitting codes.

Blind codes

These are codes that require a chart or computer program to translate the blind code to a bitting code, which is used to create the actual key. Most key codes are blind codes, and publication of code books or software are restricted to licensed locksmiths in most jurisdictions for security reasons. Some locksmiths also create their own blind coding systems for identifying key systems they installed, or for customer identification and authorization in high security systems. Example: 23N7 (General Motors) or X2100 (Nissan) are examples of blind codes used for automotive ignition keys.

Many computer-generated master keying charts also utilize blind codes for identifying individual change keys and masters within the system.

Bitting code

The translated blind code which the locksmith actually uses to cut each cut on a blank key. Example: padlock blind code W123 translates to bitting code 25313, to which the locksmith would cut the key with his code machine by setting it to 25313.