- X-10
- X-bus
- X-height
- X-rated
- X-Windows
- XA (Extended Architecture)
- XBDA (Extended BIOS Data Area)
- XBRL (eXtensible Business Reporting Language)
- XCOPY (eXtended Copy)
- XD picture card
- XDI (External Device Interface)
- XDR (eXternal Data Representation)
- XDSL
- Xeon
- Xerox
- Xerox PARC (Xerox Palo Alto Research Center)
- XEU (Xerox Encryption Unit)
- XFC (eXtended Function Call)
- Xfer
- XGA (eXtended Graphics Adapter)
- XHTML (eXtensible HyperText Markup Language)
- XID (eXchange InDentification)
- XKMS (XML Key Management Specification)
- XLink
- XLR
- XML (eXtensible Markup Language)
- XML-RPC (XML Remote Procedure Call,)
- XMM (eXtended Memory Manager)
- Xmodem
- XModem
- XMS (eXtended Memory Specification)
- XNS (Xerox Network System)
- XOR (Exclusive OR)
- XP (Extreme Programming)
- XPath
- XPointer
- XRCD (eXtened Resolution Compact Disc)
- XScale
- XSD (XML Schema Definition)
- XSL (Extensible Style Language)
- XSLT (XML Stylesheet Transformations)
- XSMD (eXtended Storage Module Drive)
- XT (eXtended Technology)
- XTP (eXpress Transfer Protocol)
- XUI (X-windows User Interface)
- XviD
- XXX
