- J-code
- J-list
- J/C
- J/J
- J/K
- J/O
- J/P
- J/W
- J2EE
- J2LYK
- J4F
- J4G
- J4T or JFT
- J5M
- jabber
- jack in
- JAD
- JAFO
- JAFS
- jaggies
- jailbreaking
- JAM
- Japanese smileys
- JAR file
- JAS
- Java
- JavaScript
- jawboning
- JC
- JDBC
- JDI
- JDK
- JDMJ
- Jealz
- JEOMK
- jerry-rig
- JFH
- JFI
- JGMB
- JHO
- JHOM
- JHOMF
- JIC
- Jini
- jitterati
- JK
- JLY
- JM2C
- JMDTP30
- JMO
- JOML
- JOOTT
- JOY
- joystick
- JP
- JPEG Optimizer
- JPG or .jpg
- JPIGs
- JS
- JSP
- JSU
- JSYK
- JT
- JTLYK
- JTOL
- JTOU
- JUADLAM
- Jughead
- juice a brick
- juice jacking
- jump page
- junk sleep
- just-in-time (JIT)
- JVM
- JW
