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Table of contents
Dex Compilers
Working of Dex Compilers
Popular Dex Compilers
DX Compilers
D8 Compilers
R8 Compilers
Frequently Asked Questions
How can a Dex Compiler optimize the code?
What is Multidexing?
What is Proguard?
Last Updated: Mar 27, 2024

What is the Function of Dex Compiler

Author Kartik Singh
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Hello Ninjas, many of us are keenly interested in Android app development. But do we really know what goes behind the making of these apps? Apart from the JAVA or Kotlin code we write, how are the packages compiled and processed?

What is the Function of Dex Compiler

Dex compilers are an integral part of Android app development. In this article, we will see what is the function of dex compiler. We will also see the different types of dex compilers and how they operate.

Dex Compilers

Dex compilers are the compiler that converts the .class bytecode into .dex bytecode. The main task is to convert the high-level programming code (JAVA or Kotlin) into Dalvik Executable(DEX) format that can run on Android platforms. The dex code is now a requirement for applications to run to work on the Android Runtime environment. 

The working of the dex compiler is abstracted. The abstracted work is responsible for many parameters associated with the Android APK. Like the  app's build time, .dex file size, and runtime performance.

Also see, Cross Compiler

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Working of Dex Compilers

The working of the dex compilers is mostly abstracted. Still, we can learn the working considering some general steps involved here.

  • Initially, a Lexical Analysis of the code is done. Here, the code is broken into smaller tokens to be read by the compiler.
  • The tokens generated are taken for syntax analysis. Here, the syntax analyzer generates a parse tree for the sequence of tokens.
  • The generated parse tree is read, and a code is generated. 
  • The generated code is based on the parse tree but not optimized.
  • The code is now optimized to get an optimized low-level code for the initial input of high-level code.
  •  The optimized code is the .bytecode that can run in the Android runtime environment.

The .bytecode generated can now be packaged with some additional files to get the APK file for the input code.

Popular Dex Compilers

Here is a list of the popular Dex Compilers used in the Information Technology World.

DX Compilers

DX or DirectX compilers are compilers that are developed by Microsoft. The DX compilers are responsible for converting the high-level programming code (JAVA or Kotlin) into Dalvik Executable(DEX) format that can run on DirectX (Android) runtime. The DX compilers consist of a list of APIs that can be used to optimize the code, detect errors and create a code for DirectX runtime.


There are several DX compilers that are used. The popular DX compilers are the Microsoft Visual C++ compiler and the LLVM-based Clang compiler. The DX compilers can be integrated with the software development kit and used effectively.

D8 Compilers

D8 is a powerful dex compiler (dexers) that are responsible for converting high-level programming code (JAVA or Kotlin) into Dalvik Executable(DEX) format that can run in an Android runtime environment. D8 comes as an inline command tool. It can also be used as an Android Gradle plugin. The above-discussed DX compilers are now replaced with D8 Compilers.


D8 is more powerful than the DX compilers. D8 offers fast compilation and a small dex file size. D8 also has better code optimization techniques and debugging capabilities.

D8 is command line integrated. It requires the path to the file to be compiled. For example

d8 path-to-input-files [options]


The [options]associated with the above code can have the following parameters.

  • - - debug 
  • - - release
  • - - output path
  • - - min - api number
  • - - file-per-class
  • - - no - desugaring

R8 Compilers

R8 is the most recent advancement in the dex compilers for Android Runtime. R8 compilers have rich functionality and provide a combination of capabilities than others. R8 compilers are enabled with Proguard and desugar functionalities. Therefore, R8 can replace both Proguard and Desugar, saving up to 25% of the dex file size. 


Proguard is a tool associated with code optimization and shrinking. By changing the Gradle properties, we can make R8 more capable.

Must Read Recursive Descent Parser and  cousins of compiler

Frequently Asked Questions

How can a Dex Compiler optimize the code?

The dex compiler can optimize the code generated after the syntactic parsing. It can use methods like removing unused code. It can combine multiple classes into one single file. It can also use shrinking to reduce the dex file size.

What is Multidexing?

The dex file is defined with a specific limit of methods. For large files, the limit might exceed, so there is a need for multidexing. Multidexing allows users to have multiple dex files corresponding to a single code. 

What is Proguard?

Proguard is a code optimization tool used in Android app development. It helps in code shrinking, thereby allowing to have small-size of APK. The main optimization it performs is eliminating unused code and resources.


In this article, we learned about what is the function of Dex compiler. We saw how it plays an integral part in Android development. It helps to bring down the app build time and increases its performance. We also learned about the different types of dex compiler and their use case. 

To learn more about compilers and compilation in Android App Development, you can check out our other blogs

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