Police code 10-4 usually means message received, understood, or acknowledged. It is one of the best-known radio codes, so scanners, dispatch logs, and public safety conversations often use it as the quick response that says the message got through.
That said, the code is still not universal. Departments can adjust their radio books, and some agencies rely more on plain language, so context matters. If you want the broader radio context, see our Police 10 Codes guide and the homepage.
What 10-4 Means
10-4 is a short acknowledgement signal. In practical terms, it lets a dispatcher or officer confirm receipt without repeating the whole message.
Common Use in Police Radio and Scanner Traffic
On the radio, 10-4 shows up when one unit checks in, confirms a request, or signals that they understand instructions. Scanner listeners hear it all the time because it is simple and widely recognized.
Plain-English Example
A dispatcher might say, “Unit 12, report to Main and 5th,” and the officer answers, “10-4.” That tells everyone the instruction was heard and understood.
Important Variation Note
Some agencies treat 10-4 as a general acknowledgment, while others reserve it for a more formal confirmation. A few departments still say it differently or avoid 10 codes entirely.
For more context, compare this with Police 10 Codes, Police Scanner Codes, and the homepage.
FAQ
Is 10-4 used everywhere?
No. It is common across many agencies, but some departments use different radio books or plain language instead. Local policy always wins.
Is 10-4 an official universal code?
Not really. It is widely recognized, but police code meanings are still shaped by department training and regional practice.
Can scanner listeners rely on 10-4?
Usually, yes, for the common public meaning of acknowledgment. Still, the safest reading is always the one that fits the agency and the conversation around it.
What other 10 codes should I learn first?
Start with 10-20 for location, 10-7 for out of service, 10-8 for in service, and 10-33 for emergency traffic. Those show up often on radio traffic and scanner pages.