What Are the 7 Different Types of Cable Connectors? A Visual and Technical Reference

Every cable has to end somewhere. The connector at each end is the part that actually makes the electrical or optical contact with the equipment, and it is what most people see and touch even when they never look at the cable itself. Seven connector families cover the overwhelming majority of cables in modern homes, offices, studios, and data centers. Learning these seven is the fastest way to look at any cable, identify what it does, and figure out where it plugs in.

1. RJ45 (8P8C) for Ethernet

The RJ45 connector is the rectangular eight-pin plastic plug at the end of every Ethernet cable. Technically the connector is 8P8C (eight positions, eight contacts), and the “RJ45” name is a slight historical misnomer, but the industry has settled on it. The plug clicks into a matching socket on routers, switches, network cards, and wall outlets. A small spring tab on top of the connector holds it in place until you squeeze it to release.

RJ45 connectors are crimped onto twisted-pair cables in either of two wiring patterns, T568A or T568B. The two patterns are functionally identical for standard Ethernet but use slightly different pair arrangements. Most modern installations use T568B for new work because it matches the older AT&T standard most installers grew up with.

The older RJ11 connector, used for landline telephones, looks similar but is smaller (six positions, two or four contacts) and is not compatible with Ethernet equipment.

2. BNC (Bayonet Neill-Concelman)

BNC is the twist-and-lock cylindrical connector you see on coaxial cables used in test equipment, professional video, and older networking. Push the connector onto the matching jack and rotate it a quarter turn to lock. The bayonet mechanism makes BNC fast to connect and disconnect while still holding firmly under vibration.

BNC connectors come in 50-ohm and 75-ohm variants. The 50-ohm version dominates radio, instrumentation, and laboratory equipment. The 75-ohm version handles professional video, including SDI and HD-SDI signals used in broadcast facilities. The two look identical but are not interchangeable at high frequencies; using a 50-ohm BNC on a 75-ohm video line causes reflections that distort the signal.

For residential cable television and satellite, the F-type screw-on connector replaced BNC decades ago because it costs less and tolerates rougher installation. F-connectors are the threaded coax connectors on the back of every modern TV, cable box, and modem.

3. USB Type-A, Type-B, and Type-C

USB has been through several connector generations, but three forms cover almost everything in current use. USB Type-A is the rectangular plug on the back of a computer or charger, the original standard since 1996. USB Type-B is the squarer plug used at the device end of older peripherals like printers and external hard drives, including its smaller mini-B and micro-B descendants. USB Type-C is the modern reversible oval connector that fits either orientation and supports the highest speeds and power deliveries.

USB-C is technically just a connector; the actual data and power protocols are negotiated between the two devices. A USB-C cable might support USB 2.0 at 480 Mbps, USB 3.2 at 20 Gbps, USB 4 at 40 Gbps, Thunderbolt 4 at 40 Gbps with PCIe tunneling, or DisplayPort Alt Mode for video. The cable’s capabilities are marked on the connector with a small symbol, though many cables are mislabeled or unlabeled.

4. HDMI

HDMI (High-Definition Multimedia Interface) connectors come in three sizes: full-size Type A (the most common), mini Type C (used on older cameras and tablets), and micro Type D (used on smartphones and small action cameras). All three carry the same signals, just in different mechanical packages. The connector has 19 pins arranged in two rows inside a trapezoidal shroud that prevents incorrect insertion.

HDMI has gone through several revisions while keeping the connector the same. HDMI 1.4 handles 4K at 30 Hz. HDMI 2.0 handles 4K at 60 Hz. HDMI 2.1 handles 8K at 60 Hz, 4K at 120 Hz, dynamic HDR, and variable refresh rate, with bandwidth up to 48 Gbps. The connector at the end of the cable does not change; the cable construction and the device firmware determine what speed combination actually works.

5. DisplayPort and Mini DisplayPort

DisplayPort is HDMI’s main competitor for computer video. The connector has 20 pins in a recessed L-shaped slot with a latch on one side that holds the cable in place. Mini DisplayPort is a smaller variant used on Apple laptops and some PC laptops, with the same electrical capabilities but a smaller mechanical form factor.

DisplayPort is generally preferred for computer-to-monitor connections because it supports higher resolutions and refresh rates earlier than HDMI did, supports multi-stream transport for daisy-chaining monitors, and uses a packet-based protocol that more closely resembles networking. DisplayPort 2.1, the current version, supports up to 80 Gbps of bandwidth, enough for 16K video.

6. Fiber Optic Connectors: LC, SC, and ST

Fiber optic cables use precision connectors that align the glass core within microns of perfect concentricity. Three connector types dominate. SC connectors have a square body with a push-pull latch and are common on telecom equipment and patch panels. LC connectors are smaller versions of SC with the same locking style; they pack twice as many connections into a rack panel and have become the modern standard for data-center fiber. ST connectors have a round bayonet body that twists like a BNC and are mostly seen on older installations.

All three connector types are available in single-mode and multimode variants, distinguished by color: yellow boots for single-mode, aqua or beige boots for multimode. Mixing connector types is possible with adapter cables but mixing single-mode and multimode fibers will not work because the cores are different sizes.

For high-density data-center work, MPO and MTP connectors gang 12 or 24 fibers into a single rectangular ferrule. These connectors enable parallel optical interfaces like 40 GbE and 100 GbE in a small footprint.

7. Audio Connectors: XLR, TRS, and RCA

Audio cables use three connector families that have remained stable for decades. XLR is the three-pin round connector used in professional audio for microphones, monitors, and interconnects. It carries balanced signals (hot, cold, and ground), which makes it immune to interference over long runs. The locking latch keeps the connector secure on a working stage.

TRS (Tip-Ring-Sleeve) is the quarter-inch or 3.5 millimeter cylindrical plug used in headphones, guitars, keyboards, and consumer audio. Two-conductor TS versions carry mono unbalanced signals; three-conductor TRS versions carry stereo or balanced mono; four-conductor TRRS versions add a microphone channel for headsets. The same connector size and shape covers all of these variants, which is why headphone jacks have become surprisingly versatile.

RCA (also called phono) connectors are the small color-coded plugs used in consumer audio and composite video. Red and white for stereo audio, yellow for video. RCA is unbalanced and noisier than XLR or balanced TRS, but it is cheap, easy to terminate, and adequate for short consumer runs.

How to Tell Them Apart

The fastest way to identify a connector is by shape. Rectangular with eight tiny gold contacts: RJ45 Ethernet. Cylindrical with a twist-lock collar: BNC or audio TRS depending on size. Flat oval with rounded ends: USB-C. Trapezoidal with 19 pins: HDMI. L-shaped slot with a latch: DisplayPort. Square with a push-pull body and a single glass strand visible: SC fiber. Three pins in a round body: XLR audio.

Once you can name the connector, you can usually deduce what kind of cable is attached to it, what speed it supports, and what equipment it plugs into. Those seven connector families cover the cables you will meet on almost any installation or repair job.