What the stamp does
A Do Not Duplicate stamp asks the person cutting keys not to copy it. Many hardware stores and key kiosks will refuse, some will not, and the key blank itself is the same common blank as any other key. The stamp makes copying a little less convenient. It does not make it impossible, and there is no record of who copied what.
What actually controls keys: restricted keyways
Real key control comes from the cylinder and the key blank, not the stamp. A restricted or patented keyway uses a key blank that is only sold to authorized dealers, who will only cut it for the registered owner of the system, usually against a signature or an ID card. Copies cannot be made at a kiosk because the kiosk cannot get the blank. That is what makes it work, and it is why restricted keys are common in offices, apartment buildings and anywhere a lost key would mean changing dozens of locks.
Our pages on high-security locks and master key systems cover how these are set up.
If you are a tenant or an employee
If a key you were given says Do Not Duplicate, ask the landlord or the office for another one rather than copying it. A copied key that turns up later can make you the first person asked when something goes missing, and many leases and employee policies say so in writing.
If you manage the keys
- Keep a written list of who has which key and when they got it.
- Rekey when a key is not returned, rather than hoping it was lost. Our guide to rekeying or replacing locks explains the difference.
- For buildings with many people coming and going, a restricted keyway or access control gives you control a stamp never will.
Questions people ask
Is it illegal to copy a Do Not Duplicate key?
The stamp itself is a request rather than a technical barrier, and many stores will refuse to copy it. Whatever the law says where you are, copying a key you were told not to copy can break your lease or your employer’s policy.
Will a locksmith copy a Do Not Duplicate key?
A careful locksmith will ask who the key belongs to and whether you are allowed to copy it. For a building key, ask the owner or manager for another one.
What is a restricted keyway?
A key blank sold only to authorized dealers, who cut it only for the registered owner of the system. It is what actually stops copies, unlike a stamp.
How do I control keys for a rental or an office?
Keep a list of who has which key, rekey when keys are not returned, and use a restricted keyway or access control where many people need access.