“Do Not Duplicate” Keys: What You Need to Know About Their Security

You may have seen keys stamped with “Do Not Duplicate” or “DND” and assumed they’re more secure than a standard key. After all, if it says not to duplicate, that should mean no one can make a copy of it… right?

Unfortunately, that little phrase is more of a polite request than an enforceable rule. Let’s talk about why—and what you can do if you need true key control.

What Does “Do Not Duplicate” Actually Mean?

When you see “Do Not Duplicate” on a key, it’s essentially a warning or a suggestion. The intention is to discourage unauthorized copies, but it doesn’t come with legal weight. Many hardware stores will honor the request and refuse to copy them… but not all. Some places might not notice, others might not care, and unless the key is protected by patent or legal restrictions, there’s nothing to stop someone from making a copy elsewhere.

Why Doesn’t It Offer More Security?

Because the key itself is often a standard blank that anyone can purchase. If someone has the key in hand, they can take it to a locksmith or use self-service kiosks that don’t check for those markings. There’s no built-in protection to prevent unauthorized duplication.

So, What Should You Do for Better Security?

If you want to ensure that no one can duplicate your keys without authorization, here’s what you should look for:

🔑 Restricted or patented key systems 

These are keys that can only be duplicated by authorized locksmiths, typically with proof of ownership and identification. The key blanks aren’t available to just anyone, and the manufacturer controls who gets them.

🔑 High-security locks

These systems often come with restricted keys as part of their design. They offer more resistance to picking, bumping, and drilling in addition to key control.

🔑 Key control policies

If you manage an office or rental property, have clear policies about who gets keys and how they are tracked. Even the best key systems need human accountability.

The Bottom Line

A key stamped “Do Not Duplicate” might make you feel better—but it won’t make you safer. If you need true control over who has access to your property, talk to a professional locksmith (like us!) about high-security locks and restricted key systems. We can help you find a solution that keeps you in control.