Angular is a popular front-end development framework that uses typescript. Angular Applications can be compiled via two processes. one is Ahead-of-Time (AOT) and the other is Just-in-Time (JIT) compilation.

Let’s understand both in detail.

AOT compilation

AOT compilation is the process of compiling the Angular application during the build process before the application is served to the users. This compilation converts the Angular templates into highly-optimized JavaScript code that can be executed by the browser more efficiently. This compiled code is smaller in size and provides better performance, especially on slower devices.

official doc link for AOT compilation.

JIT compilation

JIT compilation is the process of compiling the Angular application during runtime, as the user interacts with the application. The browser downloads the application code, compiles it, and then executes it. It provides faster build times and a better development experience, as it allows for faster iteration and debugging during development.

AOT vs JIT compilation

AOT compilation is mostly considered the more efficient compilation process. It is also much faster than the JIT compilation.

AOT compilation is better in the case of large application development.

AOT compiled code does not to recompiled on browser run time, it reduces the time of loading the application and it improves the overall performance.

But AOT takes a lot of time in the build process and it can also require some more configurations compared to the JIT compilation process.

The main advantage of JIT compilation is that it provides faster build and also flexibility. For smaller applications, JIT is a good choice, and for large applications, AOT is a good choice.

The JIT compilation process can take a lot of time during the run time, this will be no big issue if the application is small in size, but in the case of a large application, this compilation process can slow down the application’s performance.

Aot compilation improves security as well because the final build is a compiled code and this does not contain any Angular-specific syntax.

AOT vs JIT compilation both have their advantages and disadvantage, JIT compilation is generally faster and more flexible, while AOT compilation is generally more performant and secure.

So now you have quite an understanding of both the compilation process AOT and JIT. feel free to comment and share with your friends.

Also, read RxJS operators used for error handling in angular and Angular vs React full comparison.