What is armeabi and why they use it?

I see this library (armeabi) many times when I explore open sources.

I net searched for an explanation of it, but all the results I found are talking ABOUT it and not defining it.

What is this armeabi and why are they using it in Android applications?

Android devices have CPUs. Many of those CPUs are based on the ARM architecture, while some are based on x86, and a few others are based on other stuff like MIPS.

Some Android apps use the Native Development Kit (NDK) to create C/C++ code to link into their app. C/C++ code needs to be compiled for a specific CPU architecture. The NDK places the version of the C/C++ code compiled for each architecture into an architecture-specific directory. One of those directories is armeabi/, which is for a generic ARM CPU. There is also armeabi-v7/ (for an ARM v7-compatible CPU), x86/ (for x86 CPUs), etc.

ABI - Application Binary Interface

EABI - Embedded Application Binary Interface

So ARMEABI are compiled binaries matching your android device's CPU architecture.

e.g.

arm64-v8a (Nexus 5x) - 64bit - ARM Cortex-A35, ARM Cortex-A53, ARM Cortex-A57, ARM Cortex-A72, ARM Cortex-A73

armeabi-v7a - 32bit - ARM Cortex-A5, ARM Cortex-A7, ARM Cortex-A8, ARM Cortex-A9, ARM Cortex-A12, ARM Cortex-A15, ARM Cortex-A17

To include *.so binary jniLibs using Android Studio 2.3 place them in src/main/jniLibs folder and add the following configuration to your *.gradle file:

android {
    sourceSets {
        main {
            jniLibs.srcDirs = ['src/main/jniLibs']
        }
    }
}

dependencies {
    compile fileTree(dir: 'jniLibs', include: ['*.so'])
}

I did recently see a pretty good article related to the different CPU's and suggestions on how to maintain APK size while giving support for them. The article gives some info for the following:

• mips
• mips64
• X86
• X86–64
• arm64-v8a
• armeabi
• armeabi-v7a