JIT Compiler

JIT Compiler

Just-in-Time compiler. A compiler that allows programs (possibly ones compiled into an intermediate byte code) to be automatically compiled into native machine code on the fly. Java and .NET use JIT compilers.

A consequence of using a JIT Compiler is that the first use of a software resource is typically much slower than subsequent uses - because the software is compiled when it is first run. This is why a website written using .NET is slow to respond when the first page on the site is requested, but much faster thereafter.