When HarmonyOS was launched as a smartphone operating system in 2021, Ars Technica speculated that it was essentially a "rebranded version of Android and EMUI" with nearly "identical code bases". ^[1] Following the release of the HarmonyOS 2.0 beta, Ars Technica and XDA Developers suggested that "the smartphone version of the OS had been forked from Android 10". Ars Technica alleged that it resembled the existing EMUI software used on Huawei devices, but with all references to "Android" replaced by "HarmonyOS". It was also noted that the DevEco Studio software based on JetBrains open source IntelliJ IDEA IDE "shared components and tool chains" with Android Studio.

using Gradle for migration of Android development to the native app framework system newer basic HarmonyOS API infertile development in imperative Java programming with similar basic applications elements in API names with the custom OpenHarmony L3-L5 branch codebase that includes AOSP framework in the dual-framework for Android Java developers during public domestic convergence OS development stages before moving to declarative ArkUI with primary customised TypeScript-based ArkTS programming language and its own Hvigor build automation tool for its evolved DevEco Studio IDE in the later versions with apps packaged as .APP outside of Android APK packaged apps. ^{[2] [3] [4]}

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At its launch as an operating system for smartphones in 2021, HarmonyOS was, however, rumored by Ars Technica simply to be "rebranded version of Android and EMUI" with nearly "identical code bases". Following the release of the HarmonyOS 2.0 beta, Ars Technica and XDA Developers speculated that "the smartphone version of the OS had been forked from Android 10". Ars Technica alleged that it resembled the existing EMUI software used on Huawei devices, but with all references to "Android" replaced by "HarmonyOS". It was also noted that the DevEco Studio software based on JetBrains open source IntelliJ IDEA IDE "shared components and tool chains" with Android Studio.

When testing the new MatePad Pro in June 2021, Android Authority and The Verge similarly observed similarities in "behavior", including that it was possible to install apps from Android APK files on the HarmonyOS-based tablet, and to run the Android 10 easter egg apk app, reaffirming earlier rumor mills.

At its launch as an operating system for smartphones in 2021, HarmonyOS was, however, rumored by Ars Technica simply to be "rebranded version of Android and EMUI" with nearly "identical code bases". Following the release of the HarmonyOS 2.0 beta, Ars Technica and XDA Developers speculated that "the smartphone version of the OS had been forked from Android 10". Ars Technica alleged that it resembled the existing EMUI software used on Huawei devices, but with all references to "Android" replaced by "HarmonyOS". It was also noted that the DevEco Studio software based on JetBrains open source IntelliJ IDEA IDE "shared components and tool chains" with Android Studio.

When testing the new MatePad Pro in June 2021, Android Authority and The Verge similarly observed similarities in "behavior", including that it was possible to install apps from Android APK files on the HarmonyOS-based tablet, and to run the Android 10 easter egg apk app, reaffirming earlier rumor mills.

The first version of DevEco Studio 1.0 IDE, released on September 9, 2020, supported development for both EMUI 11 and HarmonyOS. This release came after Huawei had been on the United States Entity List since May 2019, which restricted Huawei's access to Google's proprietary GMS on Android. Consequently, Huawei focused on developing AOSP with EMUI for the short term and planned for a long-term migration to HarmonyOS.

DevEco Studio, based on JetBrains' open-source IntelliJ IDEA IDE, shared components and toolchains with Android Studio, using Gradle to facilitate the migration of Android development to the new native app framework of HarmonyOS. During the early stages of public development, the system used a dual-framework approach with the OpenHarmony L3-L5 branch codebase, which included the AOSP framework, making it easier for Android Java developers. Later versions of HarmonyOS introduced the declarative ArkUI with the custom TypeScript-based ArkTS programming language and its own Hvigor build automation tool, with apps packaged as .APP files instead of the Android APK format.