HDMI (High-Definition Multimedia Interface)
HDMI carries both digital video and audio over a single cable. Connector types: Type A (standard, 19-pin), Type C (Mini HDMI, 19-pin smaller), Type D (Micro HDMI, 19-pin smallest). Versions: HDMI 1.4 — 4K at 30Hz, 3D, Audio Return Channel (ARC). HDMI 2.0 — 4K at 60Hz, 18 Gbps bandwidth. HDMI 2.1 — 8K at 60Hz, 4K at 120Hz, 48 Gbps, eARC (Enhanced Audio Return Channel), Variable Refresh Rate. HDMI CEC (Consumer Electronics Control): allows one remote to control multiple HDMI-connected devices. ARC/eARC: sends audio from TV back to soundbar/receiver through the HDMI cable (eliminates separate audio cable). HDCP (High-bandwidth Digital Content Protection): DRM on HDMI — required to play protected content (Blu-ray, streaming).
DisplayPort
DisplayPort (DP) is designed primarily for computers and monitors. Standard connector: rectangular with one angled corner (not rectangular like HDMI). Mini DisplayPort (mDP): smaller version used on older Macs and Thunderbolt 1/2. Versions: DisplayPort 1.2 — 4K at 60Hz, 21.6 Gbps, daisy-chaining up to 3 monitors via MST (Multi-Stream Transport). DisplayPort 1.4 — 8K at 60Hz, HDR, 32.4 Gbps. DisplayPort 2.0/2.1 — 16K, 77 Gbps. Supports audio. Daisy-chaining: connect monitor to PC, then second monitor to first monitor's DP out (monitor must support MST hub). Adaptive Sync / G-Sync / FreeSync: variable refresh rate protocols — require DisplayPort (or HDMI 2.1). Active adapters: DP to HDMI or DP to DVI require active adapters for some configurations.
DVI (Digital Visual Interface)
DVI was the transition connector from analog VGA to digital displays. DVI types: DVI-D (digital only — most common), DVI-A (analog only), DVI-I (integrated — both digital and analog). DVI connector configurations: Single Link: up to 1920×1200 at 60Hz. Dual Link: up to 2560×1600 at 60Hz (wider connector with extra pins in center). DVI-D single link: 18+1 pins. DVI-D dual link: 24+1 pins. DVI-I single link: 18+5 pins (the +5 carries analog). DVI-I dual link: 24+5 pins. Identifying tip: DVI-D has a flat blade; DVI-A and DVI-I have a flat blade plus 4 surrounding pins. DVI does not carry audio. Largely replaced by HDMI and DisplayPort in modern hardware but common on older monitors and graphics cards.
VGA (Video Graphics Array)
VGA (DE-15 connector) is a legacy analog video interface. 15-pin, 3-row D-sub connector. Blue color-coding is common. Maximum practical resolution: 1920×1080 at 60Hz (image quality degrades significantly at high resolutions due to analog signal). No audio. No digital signal — analog means image quality is affected by cable quality and length. Still found on: older projectors, older monitors, KVM switches, legacy PCs. When an adapter from digital (HDMI/DP) to VGA is needed, an active adapter/converter is required (digital-to-analog conversion). VGA is officially deprecated and no longer included on most modern graphics cards and laptops. Identifying tip: 3 rows of 5 pins each, blue color, trapezoidal D-sub shell.
Thunderbolt Display Output
Thunderbolt 3 and 4 (USB-C connector): support up to two 4K displays or one 8K display simultaneously. Thunderbolt 3 supports DisplayPort 1.2; Thunderbolt 4 requires DisplayPort 1.4 or 2.0. Thunderbolt 1 and 2 (Mini DisplayPort connector): Thunderbolt 1 supports up to 2560×1440. Thunderbolt 2 supports 4K. USB4 (USB-C): also supports DisplayPort Alt Mode — can output video. USB-C DisplayPort Alt Mode: many USB-C ports (not Thunderbolt) support DisplayPort output via Alt Mode. Requires cable that supports Alt Mode or DP-to-USB-C adapter. Identifying tip: USB-C port with Thunderbolt outputs lightning bolt icon + monitor icon.
Adapter and Conversion Considerations
Passive adapters (no conversion electronics): work for same-signal conversions. HDMI to DVI-D: passive adapter works (both digital, no audio on DVI). DisplayPort to HDMI: may need active adapter depending on GPU. DVI-A to VGA: passive (both analog). Active adapters (contain conversion electronics): required for digital-to-analog. HDMI to VGA: requires active adapter. DisplayPort to VGA: requires active adapter. Single-link vs dual-link DVI matters when adapting — dual-link supports higher resolutions. USB-C to HDMI/DP: usually passive if the USB-C port supports Alt Mode. KVM switches: allow one keyboard/video/mouse set to control multiple computers — important to match the video connector type. Resolution and refresh rate may be limited by the weakest link in the chain (cable, adapter, monitor, GPU).