Depending on the model of your motherboard, you might have noticed a little seven-segment display, usually in the upper right corner. When you turn the PC on, you will see that this display cycles through a load of seemingly random combinations of letters and numbers before settling on a single code.
This example shows the Debug LED display from a Z890 AORUS XTREME AI TOP. Most of the time the display is a lot less fancy than this.
What are Motherboard Post Codes?
However, these codes are not random. In fact, they are a massively helpful diagnostic tool known as “POST Codes”, “Debug LEDs”, “Error Codes” or some variation like that, depending on the brand of the motherboard in question. Each time you turn the computer on, the motherboard cycles through these POST (Power-On Self-Test) codes as it checks that everything is working as intended.
If there is something wrong, then the computer will in most cases refuse to boot up, and the motherboard will display the code corresponding to the issue it has detected. This is helpful, as you can then look that code up in the motherboard manual and it will tell you what's wrong.
If your PC is functioning correctly, then the display will either go blank or the code that means everything is fine.
The POST code LED display is located in the top-right corner of the MSI MAG Z890 TOMAHAWK WIFI motherboard.
An Example Gigabyte X570 AORUS MASTER. In this case "9E" is a reserved code for future use, meaning that nothing is wrong.
Motherboard Error Codes Explained
Each brand of motherboard has its own set of codes and associated meanings, and sometimes these codes can vary within a brand’s own lineup, depending on the chipset, motherboard form factor, and many other things.
The solution here is to find the manual that should be in your motherboard’s box and flip through to the glossary of POST codes usually found at the back. Here you’ll find out what each code means which will point you in the right direction.
If you no longer have the motherboard manual, you can find a PDF version of the manual from the product page of your motherboard manufacturer's website. It will usually be under a tab labelled “Support” or “Downloads”.
Can’t remember the exact model of your motherboard? We wrote a guide on finding out which motherboard you have, so read that to find out.