10-4 – Meaning, Origin and Usage

Are you looking for a confirmation response to tell your friend that you understand their request? You could always use “10-4” to show them you get what they are saying. The “10-4” code appears in media and movies, and you probably hear it all the time, but what does it mean?

This post unpacks everything you need to know about the meaning, origin, and use of this term in conversation.


10-4” is a part of the “ten code” terms used in law enforcement and the military, as well as in truck driver communications. When you say “10-4”, you’re using it as a confirmation that you received information from another party, and you are acting on that information.

Typically, most people who use the phrase will be using it with other people who understand the term in official law enforcement or military situations. “10-4” means that you know what the person is saying, and it often features the phrase, “10-4 copy.”

Copy” is another way of saying that you receive and understand the information in the communication. However, 10-4 and copy are essentially the same terms, and saying “copy” after “10-4” is somewhat redundant. Still, people will use it to impress that they received the request or information and understand the context of the request.

Example Usage

Rowan: “Are you headed to my house now, Ray?”

Ray: “10-4 good buddy, I’ll see you in a minute.”

Seb: “All units, be advised, we have an armed criminal in the neighborhood, last seen driving a blue Pontiac.”

Shane: “10-4 copy; we’re searching the area for the suspect right now.”

Bruce: “Are you on your way to the meeting at the office, Theo?”

Theo: “10-4, I’ll be there on time; the traffic is backed up right now.”


The term “10-4” originates from the CB-radio culture of the 1970s. Hollywood films promoted the use of CB radios in films like “smokey and the Bandit” and “Cannonball Run.” “CB” stands for “citizens band,” with the biggest user base found in the trucking industry.

As the use of CB radios spread, it started a subculture where CB operators were a tight-knit group of individuals, spending their time communicating with each other over the airwaves. Along with private users, CB networks were widely adopted by law enforcement and medical services as a means of stable communications.

With the rise of law enforcement using CB, the advent of “10-codes” started after World War II. The first set of 10-codes implemented by law enforcement occurred in 1940, with the Association of Public Safety Communication Officials (APC) setting the guidelines for the codes.

The original use of 10-codes was to keep communications private and reduce the need for conversation intense, adrenaline-fueled situations.

Phrases Similar to 10-4

  • I got you.
  • I understand.
  • Sure, no problem.

Phrases Opposite to 10-4

  • I didn’t hear that.
  • I didn’t catch that.
  • What are you talking about?

What is the Correct Saying?

  • 10-4.
  • 10-4 copy.
  • 10-4 good buddy.

Ways People May Say 10-4 Incorrectly

Some people may confuse the 10-4 code with other codes like 187, the police code for homicide. It’s also unsuitable for conversations where the other person doesn’t understand the 10-code lingo.

Acceptable Ways to Phrase 10-4

You can use 10-4 when telling someone that you understand their request and you’re working on a solution. You can also use the phrase when confirming another person’s request. The term is suitable for military, law enforcement, and civilian applications. Typically, you’ll use the term in civilian situations when confirming you received their instruction or request.

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