# What is Just-in-Time Compilation?

*Development · Last updated: October 27, 2026*

> Just-in-Time Compilation

It is a method of accelerating the program code by translating it into machine language at the moment it will be executed, rather than beforehand.

## Overview

Normally, the code is translated once after it is written, but this method analyzes the code while it is running and optimizes the most frequently used parts at that moment. In this way, programs remain flexible and exhibit high performance. Modern browsers and many programming languages ​​use this technology.

***Analogy:** It's like cooking the food fresh right when you sit at the table, instead of making it in advance and keeping it waiting.*

## How it works

At runtime, the performance of the code is monitored and critical parts are transformed to run faster.

## Where it is used

It is found in JavaScript engines, Java virtual machines, and modern runtime environments.

## Commonly confused with

It differs from the traditional compilation method, where the code is completely translated at the beginning, with its dynamism at run time.

## Questions and answers

**Why isn't everything JIT?**

Because it may introduce some overhead at startup, sometimes it is more advantageous to compile it beforehand.

**Does it increase performance?**

Yes, it significantly increases speed, especially in frequently repeated code blocks.

## Related terms

- [Compiler](https://trescout.com/en/dictionary/compiler/)
- [Runtime](https://trescout.com/en/dictionary/runtime/)
- [Compilation](https://trescout.com/en/dictionary/compilation/)

This explanation was written in plain language for TreScout with AI and **machine-translated** from the Turkish original · the Turkish version prevails. If something looks wrong or missing, write to [hello@trescout.com](mailto:hello@trescout.com). [Read in Turkish →](https://trescout.com/dictionary/jit-compilation/)

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Source: TreScout Dictionary · https://trescout.com/en/dictionary/jit-compilation/