Write once, run anywhere (WORA), or sometimes write once, run everywhere (WORE), is a 1995 slogan from Sun Microsystems to describe the cross-platform software benefits of the Java programming language. It refers to how compiled bytecode from Java source code can run on any system with a compatible Java virtual machine (JVM). In reality, there can be subtle differences in how a program executes due to variability in JVM implementation and host operating system which lead to the comical slogan: Write once, debug everywhere.

As Java has achieved popularity, the installation of a JVM on chips, devices, and software packages became an industry standard practice.

See also