What Plugs Into a Computer: Power, USB, Display and Audio Ports
Quick answer / TL;DR: Things that plug into a computer: the C13 power cord, USB devices, HDMI or DisplayPort video, a 3.5mm audio jack, and an Ethernet cable – almost all into the rear panel. This port map says where each goes and which one matters most.
New users face the back of a desktop for the first time and see a wall of ports: which hole takes the power cord, which takes the monitor, which takes the headset? The layout looks random, but it follows a simple logic.
This is the plain-English port map: what plugs into a computer, where each connector lives, and the few gotchas – GPU versus motherboard video port, mic versus headphone jacks – that cause most first-plug problems.
The Rear Panel, Group by Group
Power
The C14 inlet takes the C13 power cord, sitting next to the PSU rocker switch. On compact PCs it may be the smaller C6 inlet with a C5 cord. Nothing else in this group carries mains voltage – the power cord is the only high-voltage connection, and it is the one to connect with the PSU switch off.
Video
The GPU ports – HDMI, DisplayPort, sometimes USB-C – sit in a horizontal row above the motherboard ports. If the system has a discrete graphics card, the monitor plugs into this row. Plugging into the similar-looking motherboard ports below it is the classic black-screen mistake.
Data and network
USB-A ports (rectangular) take flash drives, keyboards, mice, webcams and USB speakers; USB-C ports (oval) take modern drives, docks and some headsets. The rectangular RJ45 port takes the Ethernet cable. Front-panel versions of all of these exist for convenience, but the rear ports are more reliable and faster.
Audio
The 3.5mm round jacks are color-coded: green for headphones or speakers, pink for the microphone, blue for line-in. When the system has a single combo jack, one port takes both the headset mic and the earpiece. A USB headset skips the jacks entirely and uses any USB port.
| Port | Plugs in | Location | Gotcha |
|---|
| C14 inlet | C13 power cord | Rear, by PSU switch | Connect with PSU off |
| GPU video | HDMI or DisplayPort | Rear, top row | Not the motherboard row |
| USB-A / USB-C | Drives, keyboard, dock | Rear and front | Rear is more reliable |
| RJ45 | Ethernet cable | Rear | Link lights show life |
| 3.5mm jacks | Headset, speakers | Rear, color-coded | Green out, pink in |
USB, HDMI, DisplayPort, 3.5mm and Ethernet cables matching every port above are stocked in standard lengths; the catalog groups them by the port they serve.
The Three First-Plug Gotchas
- Video cable in the motherboard port instead of the GPU – black screen while all fans spin
- Headset in the line-in (blue) jack – you hear nothing and the other side hears nothing
- USB device in a front port that is unpowered on that case – try a rear port first
Real-World Applications
First setup for a new user: power cord in with the switch off, HDMI into the top GPU row, headset into the green jack, Ethernet into RJ45, USB keyboard and mouse – done. Tech support triage: when a remote user reports no display, the first question is which row the HDMI went into. Kiosk and lab builds: label the rear panel with the intended cable per port so the next technician does not have to re-learn the layout.
Related reading: The setup order: how to plug in a computer step by step — how-to-plug-in-a-computer
Related reading: Charging peripherals: the Micro USB power cable for older USB devices — micro-usb-power-cable
Frequently Asked Questions
What plugs into the back of a computer?
The C13 power cord, the monitor video cable (HDMI or DisplayPort), the Ethernet cable, USB devices, and the 3.5mm audio jacks for headset and speakers. Front-panel versions of USB and audio exist, but the rear panel is where power, video and network always live.
Why is my monitor black even though everything is plugged in?
Check the video cable first: with a discrete graphics card it must go into the GPU ports in the top row, not the similar motherboard ports below. Then confirm the monitor is on the right input and the PSU switch is on.
Which jack do I use for a headset?
The green 3.5mm jack for the earpiece and the pink one for the microphone, if they are separate. If there is a single combo jack, the headset plugs into that one. A USB headset uses any USB port and skips the jacks entirely.
Can anything dangerous plug into a computer?
Only the power cord carries dangerous voltage – that is why it has its own keyed inlet and why it is the one connection made with the PSU switch off. Every other port (USB, HDMI, audio, Ethernet) carries low-voltage signals and is safe to connect at any time.
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